diff --git "a/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" "b/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" --- "a/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" +++ "b/raw_rss_feeds/https___arxiv_org_rss_quant_ph.xml" @@ -7,1582 +7,1824 @@ http://www.rssboard.org/rss-specification en-us - Fri, 12 Dec 2025 05:00:05 +0000 + Fri, 19 Dec 2025 05:00:09 +0000 rss-help@arxiv.org - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 Saturday Sunday - Deep Thermalization and Measurements of Quantum Resources - https://arxiv.org/abs/2512.09999 - arXiv:2512.09999v1 Announce Type: new -Abstract: Quantum resource theories (QRTs) provide a unified framework for characterizing useful quantum phenomena subject to physical constraints, but are notoriously hard to assess in experimental systems. In this letter, we introduce a unified protocol for quantifying the resource-generating power (RGP) of arbitrary quantum evolutions applicable to multiple QRTs. It is based on deep thermalization (DT), which has recently gained attention for its role in the emergence of quantum state designs from partial projective measurements. Central to our approach is the use of projected ensembles, recently employed to probe DT, together with new twirling identities that allow us to directly infer the RGP of the underlying dynamics. These identities further reveal how resources build up and thermalize in generic quantum circuits. Finally, we show that quantum resources themselves undergo deep thermalization at the subsystem level, offering a complementary and another experimentally accessible route to infer the RGP. Our work connects deep thermalization to resource quantification, offering a new perspective on the essential role of various resources in generating state designs. - oai:arXiv.org:2512.09999v1 + Relational Emergent Time for Quantum System: A Multi-Observer, Gravitational, and Cosmological Framework + https://arxiv.org/abs/2512.15789 + arXiv:2512.15789v1 Announce Type: new +Abstract: We present a relational framework in which temporal structure is not fundamental but emerges from correlations within a globally stationary quantum state. Each subsystem includes an internal clock, and conditional states evolve effectively with respect to these internal readings. The construction naturally extends to relativistic motion, gravitational redshift, and cosmological expansion, leading to a unified emergent-time functional valid across diverse physical regimes. The theory reproduces classical time dilation, predicts correlation-dependent deviations from standard evolution, and suggests that non-interacting or massless particles exhibit negligible internal time. These consequences open directions for conceptual and experimental investigations in the foundations of temporal physics, from multi-clock quantum systems to precision metrology and cosmological settings. In particular, the framework suggests measurable deviation from standard quantum evolution for highly entangled systems and predicts negligible internal time for massless particles. + oai:arXiv.org:2512.15789v1 quant-ph - cond-mat.dis-nn - cond-mat.stat-mech - hep-th - nlin.CD - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Naga Dileep Varikuti, Soumik Bandyopadhyay, Philipp Hauke - - - A Unified Linear Algebraic Framework for Physical Models and Generalized Contextuality - https://arxiv.org/abs/2512.10000 - arXiv:2512.10000v1 Announce Type: new -Abstract: We develop a bottom-up, statistics-first framework in which the full probabilistic content of an operational theory is encoded in its matrix of conditional outcome probabilities of events (COPE). Within this setting, five model classes (preGPTs, GPTs, quasiprobabilistic, ontological, and noncontextual ontological) are unified as constrained factorizations of the COPE matrix. We identify equirank factorizations as the structural core of GPTs and noncontextual ontological models and establish their relation to tomographic completeness. This yields a simple, model-agnostic criterion for noncontextuality: an operational theory admits a noncontextual ontological model if and only if its COPE matrix admits an equirank nonnegative matrix factorization (ENMF). Failure of the equirank condition in all ontological models therefore establishes contextuality. We operationalize rank separation via two complementary methods provided by the linear-algebraic framework. First, we use ENMF to interpret noncontextual ontological models as nested polytopes. This allows us to establish that the boxworld operational theory is ontologically contextual. Second, we apply techniques from discrete mathematics to derive a lower bound on the ontological dimensionality of COPE matrices exhibiting sparsity patterns, and use this bound to establish a new proof that a discrete version of qubit theory exhibits ontological contextuality. By reframing contextuality as a problem in matrix analysis, our work provides a unified structure for its systematic study and opens new avenues for exploring nonclassical resources. - oai:arXiv.org:2512.10000v1 - quant-ph - math-ph - math.MP - Fri, 12 Dec 2025 00:00:00 -0500 - new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Farid Shahandeh, Theodoros Yianni, Mina Doosti + http://creativecommons.org/licenses/by/4.0/ + Amir Hossein Ghasemi - Broadband Spatio-Spectral Mode Conversion via Four-Wave Mixing - https://arxiv.org/abs/2512.10045 - arXiv:2512.10045v1 Announce Type: new -Abstract: We introduce a framework for scalable and broadband free-space phase-matched four-wave mixing in ring resonators. This method for four-wave mixing reduces the complexity of coupling an emitter to a quantum network by combining the spatial and spectral interfaces between them into one nonlinear optical process. The device is compliant with current heterogeneous integration capabilities and has a bandwidth of 165 nm for efficient spatio-spectral conversion. We outline a fabrication-ready diamond-on-insulator pathway towards modular unit cells that natively bridge visible color centers to the infrared spectrum for scalable quantum networks. We also present and analyze an end-to-end framework for considering single-photon coupling efficiency from a color center to a quantum network. This framework represents a step forwards in analyzing and reducing system-scale losses in a spin-photon interface. - oai:arXiv.org:2512.10045v1 + Geometric Latent Space Tomography with Metric-Preserving Autoencoders + https://arxiv.org/abs/2512.15801 + arXiv:2512.15801v1 Announce Type: new +Abstract: Quantum state tomography faces exponential scaling with system size, while recent neural network approaches achieve polynomial scaling at the cost of losing the geometric structure of quantum state space. We introduce geometric latent space tomography, combining classical neural encoders with parameterized quantum circuit decoders trained via a metric-preservation loss that enforces proportionality between latent Euclidean distances and quantum Bures geodesics. On two-qubit mixed states with purity 0.85--0.95 representing NISQ-era decoherence, we achieve high-fidelity reconstruction (mean fidelity $F = 0.942 \pm 0.03$) with an interpretable 20-dimensional latent structure. Critically, latent geodesics exhibit strong linear correlation with Bures distances (Pearson $r = 0.88$, $R^2 = 0.78$), preserving 78\% of quantum metric structure. Geometric analysis reveals intrinsic manifold dimension 6.35 versus 20 ambient dimensions and measurable local curvature ($\kappa = 0.011 \pm 0.006$), confirming non-trivial Riemannian geometry with $O(d^2)$ computational advantage over $O(4^n)$ density matrix operations. Unlike prior neural tomography, our geometry-aware latent space enables direct state discrimination, fidelity estimation from Euclidean distances, and interpretable error manifolds for quantum error mitigation without repeated full tomography, providing critical capabilities for NISQ devices with limited coherence times. + oai:arXiv.org:2512.15801v1 quant-ph - physics.app-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Helaman Flores, Mahmoud Jalali Mehrabad, Siavash Mirzaei-Ghormish, Ryan M. Camacho, Dirk Englund + http://creativecommons.org/licenses/by-nc-nd/4.0/ + S. M. Yousuf Iqbal Tomal, Abdullah Al Shafin - Quantumness via Discrete Structures - https://arxiv.org/abs/2512.10063 - arXiv:2512.10063v1 Announce Type: new -Abstract: Quantum theory departs from classical probabilistic theories in foundational ways. These departures--termed quantumness here--power quantum information and computation. This thesis charts the role of discrete structures in assessing quantumness, synthesizing elements of my postdoctoral research through this lens. After an introduction to the necessary background concepts, I present my work under three broad categories. First, I present work on contextuality that extensively relies on (undirected) graphs and hypergraphs as the discrete structures of interest; more specifically, it relies on invariants associated with them. This work includes Kochen-Specker (KS) contextuality and its operationalization to generalized contextuality, expressed via (hyper)graph-theoretic frameworks. I also present work on KS-contextuality in multiqubit systems and an application of generalized contextuality to a one-shot communication task, both of which rely on hypergraphs. Second, I present work on causality, where the discrete structures of interest are directed graphs. This includes work on indefinite causal order, specifically its connections to the gap between local operations and classical communication (LOCC) and separable operations (SEP), and a device-independent notion of nonclassicality--termed antinomicity--that generalizes Bell nonlocality without global causal assumptions. Finally, I present work on the incompatibility of quantum measurements, its connection to Bell nonlocality, and its role in discriminating between quantum and almost quantum correlations in the single-system setting. The discrete structures of interest here are hypergraphs that model joint measurability relations between quantum measurements. I conclude with a summary and an overview of work that is not covered in this thesis. - oai:arXiv.org:2512.10063v1 + Optimization Techniques in Quantum Information + https://arxiv.org/abs/2512.15831 + arXiv:2512.15831v1 Announce Type: new +Abstract: This thesis focuses on the intersection of mathematical and computational optimization and quantum information. Main contributions are open-source software code: A hybrid approach mixing "traditional" nonconvex and convex methods can make difficult problems more accessible. A demonstration of how to efficiently implement such an algorithm, avoiding interfacial bottlenecks, is provided, finding optimal protocols to establish entanglement through a lossy channel. The central software package developed addresses polynomial optimization problems. Many problems naturally involve only a polynomial objective and constraint polynomials. Such problems can automatically be cast into semidefinite programs that provide a hierarchy of outer approximations. The resulting problems are often so large and scale so unfavorably with respect to the variable number and degree involved that the boundary of the doable is reached quickly. However, technical progress both in hardware and algorithms has pushed this boundary - but software frameworks for polynomial optimization have not followed in the same manner, often now making them the bottleneck that before was the solver. The package PolynomialOptimization.jl developed during this thesis aims to fill the gap and provide a very resource-efficient intermediate layer together with a wide number of algorithms to reduce the problem size, and naturally supporting complex numbers and semidefinite constraints ubiquitous in quantum information problems. Its application on an entanglement distribution problem is demonstrated, showing that even relaxations with semidefinite matrices of three- and four-digit size can be solved conveniently. Finally, a new way to calculate interior-point barriers for the cone of sums-of-squares matrices in a nearly time-optimal way is developed, whose efficient implementation has the potential of further reducing resource consumption. + oai:arXiv.org:2512.15831v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + math.OC + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ravi Kunjwal + http://creativecommons.org/licenses/by-sa/4.0/ + 10.18725/OPARU-58732 + Benjamin Desef - Gradient projection method and stochastic search for some optimal control models with spin chains. I - https://arxiv.org/abs/2512.10093 - arXiv:2512.10093v1 Announce Type: new -Abstract: This article (I) considers the known optimal control model of a quantum information transfer along a spin chain with controlled external parabolic magnetic field, with an arbitrary length. The article adds certain lower and upper pointwise constraints on controls, adds the problem of keeping the signal at the last spin, considers various classes of controls. For these problems under piecewise continuous controls, the projection-type linearized Pontryagin maximum principle, gradient projection method's constructions in its one- and two- and three-step forms were adapted by analogy with [Morzhin O.V., Pechen A.N. J. Phys. A: Math. Theor., 2025]. Moreover, an example with a genetic algorithm's successful use under a special class of controls is given. - oai:arXiv.org:2512.10093v1 + Low-Latency FPGA Control System for Real-Time Neural Network Processing in CCD-Based Trapped-Ion Qubit Measurement + https://arxiv.org/abs/2512.15838 + arXiv:2512.15838v1 Announce Type: new +Abstract: Accurate and low-latency qubit state measurement is critical for trapped-ion quantum computing. While deep neural networks (DNNs) have been integrated to enhance detection fidelity, their latency performance on specific hardware platforms remains underexplored. This work benchmarks the latency of DNN-based qubit detection on field-programmable gate arrays (FPGAs) and graphics processing units (GPUs). The FPGA solution directly interfaces an electron-multiplying charge-coupled device (EMCCD) with the subsequent data processing logic, eliminating buffering and interface overheads. As a baseline, the GPU-based system employs a high-speed PCIe image grabber for image input and I/O card for state output. We deploy Multilayer Perceptron (MLP) and Vision Transformer (ViT) models on hardware to evaluate measurement performance. Compared to conventional thresholding, DNNs reduce the mean measurement fidelity (MMF) error by factors of 1.8-2.5x (one-qubit case) and 4.2-7.6x (three-qubit case). FPGA-based MLP and ViT achieve nanosecond- and microsecond-scale inference latencies, while the complete single-shot measurement process achieves over 100x speedup compared to the GPU implementation. Additionally, clock-cycle-level signal analysis reveals inefficiencies in EMCCD data transmission via Cameralink, suggesting that optimizing this interface could further leverage the advantages of ultra-low-latency DNN inference, guiding the development of next-generation qubit detection systems. + oai:arXiv.org:2512.15838v1 quant-ph - math.OC - Fri, 12 Dec 2025 00:00:00 -0500 + cs.AR + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Oleg V. Morzhin + Binglei Lou, Gautham Duddi Krishnaswaroop, Filip Wojcicki, Ruilin Wu, Richard Rademacher, Zhiqiang Que, Wayne Luk, Philip H. W. Leong - Programmable Quantum Photonic Interfaces for Quantum Networking - https://arxiv.org/abs/2512.10140 - arXiv:2512.10140v1 Announce Type: new -Abstract: Quantum networks require interfaces translating memory photons to telecom wavelengths while controlling spatial modes; tasks performed by separate components today. We present a programmable alternative: a structured pump writes a virtual Bragg grating enabling simultaneous spatio-spectral conversion and real-time controlling of emission. Using a LiNbO$_3$ whispering-gallery resonator, we demonstrate 93\% spatial coupling and bidirectional conversion between 736\,nm and 1347\,nm. This reconfigurable interface eliminates cascaded losses and hardware modifications. - oai:arXiv.org:2512.10140v1 + Efficient Simulation of Sparse, Non-Local Fermion Models + https://arxiv.org/abs/2512.15843 + arXiv:2512.15843v1 Announce Type: new +Abstract: Efficient simulation of interacting fermionic systems is a key application of near-term quantum computers, but is hindered by the overhead required to encode fermionic operators on qubit hardware. Here, we consider models with $N$ fermionic modes in which each participates in at most a constant number $d$ of interactions and study the circuit depth required to implement the Trotterized time evolution on qubit hardware with all-to-all connectivity. We introduce an encoding that augments each physical fermionic mode with a small number of auxiliary fermions, enabling the removal of Jordan--Wigner strings. Although the preparation of the auxiliary fermion state incurs an initial overhead, this state remains invariant under time evolution. As a result, long-time evolution can be implemented with asymptotically optimal circuit depth, reducing a previously multiplicative $O(\log N)$ overhead to an additive overhead. Our results thus establish that the simulation of sparse fermionic models on qubit hardware matches the performance achievable on ideal fermionic hardware up to constant factors and $O(dN)$ ancillary qubits. + oai:arXiv.org:2512.15843v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Siavash Mirzaei-Ghormish, Mahmoud Jalali Mehrabad, Helaman Flores, Dirk Englund, Ryan M. Camacho + http://creativecommons.org/licenses/by/4.0/ + Reinis Irmejs, J. Ignacio Cirac - Engineer coherent oscillatory modes in Markovian open quantum systems - https://arxiv.org/abs/2512.10144 - arXiv:2512.10144v1 Announce Type: new -Abstract: We develop a novel framework to engineer persistent oscillatory modes in Markovian open quantum systems governed by a time-independent Lindblad master equation. We show that oscillatory modes can be created when the Hamiltonian and jump operator can be expressed in the same block-diagonal form. A key feature of the framework is that the dissipator of the Lindblad master equation are generally non-zero. We identify the weak and strong conditions, where the onset of the oscillatory modes is dependent and independent of the parameters of the system, respectively. Our method extends beyond the typical decoherence-free subspace approach, in which the dissipator is zero. We demonstrate the applicability of this framework using various models, showing how carefully tailored system-environment interactions can produce sustained coherent oscillations. - oai:arXiv.org:2512.10144v1 + Solvable Quantum Circuits from Spacetime Lattices + https://arxiv.org/abs/2512.15871 + arXiv:2512.15871v1 Announce Type: new +Abstract: In recent years dual-unitary circuits and their multi-unitary generalizations have emerged as exactly solvable yet chaotic models of quantum many-body dynamics. However, a systematic picture for the solvability of multi-unitary dynamics remains missing. We present a framework encompassing a large class of such non-integrable models with exactly solvable dynamics, which we term \emph{completely reducible} circuits. In these circuits, the entanglement membrane determining operator growth and entanglement dynamics can be characterized analytically. Completely reducible circuits extend the notion of space-time symmetry to more general lattice geometries, breaking dual-unitarity globally but not locally, and allow for a rich phenomenology going beyond dual-unitarity. As example, we introduce circuits that support four and five directions of information flow. We derive a general expression for the entanglement line tension in terms of the pattern of information flow in spacetime. The solvability is shown to be related to the absence of knots of this information flow, connecting entanglement dynamics to the Kauffman bracket as knot invariant. Building on these results, we propose that in general non-integrable dynamics the curvature of the entanglement line tension can be interpreted as a density of information transport. Our results provide a new and unified framework for exactly solvable models of many-body quantum chaos, encompassing and extending known constructions. + oai:arXiv.org:2512.15871v1 quant-ph - cond-mat.quant-gas - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + nlin.SI + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Chun Hei Leung, Pak-Tik Fong, Tianyi Yan, Weibin Li + Michael A. Rampp, Suhail A. Rather, Pieter W. Claeys - Upper Bounds on Fluctuation Growths of Observables in Open Quantum Systems - https://arxiv.org/abs/2512.10153 - arXiv:2512.10153v1 Announce Type: new -Abstract: The upper bounds for the rate of fluctuation growth of an observable in both open and closed quantum systems have been studied actively recently. In our recent work we showed that the rate of fluctuation growth for an observable in a closed quantum system is upper bounded by the fluctuation of its corresponding velocity-like observable. That bound also indicated a tradeoff between the time derivatives of the mean and the standard deviation. In this paper we will look at open quantum systems in two cases. For the first case we find the generator of evolution for an open system employing both the Taylor expansion and the standard time-ordered evolution via the Dyson series, while in the second case we consider no specific information about the evolution of the system. We then find the rate of fluctuation growth in each case. Comparing the upper bounds for each case and considering the upper bound found for a closed system suggest that including more details by separating the contributions of the system and state dynamics seems to result in looser bounds for the rate of fluctuation growth. - oai:arXiv.org:2512.10153v1 + On the power of moving quantum sensors: fully flexible and noise-resilient sensing + https://arxiv.org/abs/2512.15876 + arXiv:2512.15876v1 Announce Type: new +Abstract: We show that a single moving quantum sensor provides complete access to spatially correlated scalar fields. We demonstrate that with either trajectory or internal state control, one can selectively measure any linear functional, e.g. a gradient or a spatial Fourier series coefficient, while successfully eliminating {\it all} noise signals with orthogonal spatial correlation. This even exceeds the capabilities of a sensor network consisting of multiple entangled, yet spatially fixed, quantum sensors, where the number of suppressed noise signals is limited by the number of sensor positions. We show that one can achieve an improved scaling of the quantum Fisher information for moving sensors beyond the static fundamental limit of $T^2$. + oai:arXiv.org:2512.15876v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Newshaw Bahreyni, Paul M. Alsing, Carlo Cafaro, Walid Redjem, Christian Corda + http://creativecommons.org/licenses/by/4.0/ + Paul Aigner, Wolfgang D\"ur - Eight-Qubit Operation of a 300 mm SiMOS Foundry-Fabricated Device - https://arxiv.org/abs/2512.10174 - arXiv:2512.10174v1 Announce Type: new -Abstract: Silicon spin qubits are a promising candidate for quantum computing, thanks to their high coherence, high controllability and manufacturability. However, the most scalable complementary metal-oxide-semiconductor (CMOS) based implementations have so far been limited to a few qubits. Here, to take a step towards large scale systems, we tune and coherently control an eight-dot linear array of silicon spin qubits fabricated in 300 mm CMOS-compatible foundry process, establishing operational scalability beyond the two-qubit regime. All eight qubits are successfully tuned and characterized as four double dot pairs, exhibiting Ramsey dephasing times $T_2^*$ up to 41(2) $\mu$s and Hahn-echo coherence times $T_2^{\mathrm{Hahn}}$ up to 1.31(4) ms. Readout of the central four qubits is achieved via a cascaded charge-sensing protocol, enabling simultaneous high-fidelity measurements of the entire multi-qubit array. Additionally, we demonstrate a two-qubit gate operation between adjacent qubits with low phase noise. We demonstrate here that we can scale silicon spin qubit arrays to medium-sized arrays of 8 qubits while maintaining coherence of the system. - oai:arXiv.org:2512.10174v1 + Anticoncentration and State Design of Doped Real Clifford Circuits and Tensor Networks + https://arxiv.org/abs/2512.15880 + arXiv:2512.15880v1 Announce Type: new +Abstract: We investigate the statistical properties of orthogonal, or real, Clifford circuits doped with magic and imaginary resources. By developing the Weingarten calculus for the real Clifford group, we derive the exact overlap distribution of real stabilizer states, identifying a new universality class: the orthogonal Clifford Porter-Thomas distribution. We prove that local real architectures recover this global statistic in logarithmic depth. Furthermore, we uncover a sharp hierarchy in resource requirements: while retrieving Haar statistics necessitates a polylogarithmic amount of magic states, recovering the full unitary Clifford statistics requires only a single phase gate. + oai:arXiv.org:2512.15880v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Andreas Nickl, Nard Dumoulin Stuyck, Paul Steinacker, Jesus D. Cifuentes, Santiago Serrano, MengKe Feng, Ensar Vahapoglu, Fay E. Hudson, Kok Wai Chan, Stefan Kubicek, Julien Jussot, Yann Canvel, Sofie Beyne, Yosuke Shimura, Roger Loo, Clement Godfrin, Bart Raes, Sylvain Baudot, Danny Wan, Arne Laucht, Chih-Hwan Yang, Wee Han Lim, Andre Saraiva, Christopher C. Escott, Kristiaan De Greve, Andrew S. Dzurak, Tuomo Tanttu + http://creativecommons.org/licenses/by/4.0/ + Beatrice Magni, Markus Heinrich, Lorenzo Leone, Xhek Turkeshi - Simultaneous Classical and Quantum Communications: Recent Progress and Three Challenges - https://arxiv.org/abs/2512.10176 - arXiv:2512.10176v1 Announce Type: new -Abstract: A critical aspect of next-generation wireless networks is the integration of quantum communications to guard against quantum computing threats to classical networks. Despite successful experimental demonstrations, integrating quantum communications into the classical infrastructure faces substantial challenges, including high costs, compatibility issues, and extra hardware deployment to accommodate both classical and quantum communication equipment. To mitigate these challenges, we explore novel protocols that enable simultaneous classical and quantum communications, relying on a single set of transceivers to jointly modulate and decode classical and quantum information onto the same signal. Additionally, we emphasize extending quantum communication capabilities beyond traditional optical bands into the terahertz, even possibly to millimeter-wave and microwave frequencies, thereby broadening the potential horizon of quantum-secure applications. Finally, we identify open problems that must be addressed to facilitate practical implementation. - oai:arXiv.org:2512.10176v1 + Noncooperative Quantum Networks + https://arxiv.org/abs/2512.15884 + arXiv:2512.15884v1 Announce Type: new +Abstract: Existing protocols for quantum communication networks usually assume an initial allocation of quantum entanglement resources, which are then manipulated through local operations and classical communication (LOCC) to establish high-fidelity entanglement between distant parties. It is generally held that the resulting fidelity would increase monotonically with the entanglement budget. Here, we show that for noncooperative LOCC protocols, the resulting fidelity may decrease as more entanglement is added to a network with non-pure states. This effect results from a quantum analog of selfish routing and constitutes a potential obstacle to the optimal use of resources in large quantum networks. + oai:arXiv.org:2512.15884v1 quant-ph - eess.SP - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.dis-nn + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - 10.1109/MNET.2025.3643793 - Phuc V. Trinh, Shinya Sugiura, Carlo Ottaviani, Chao Xu, Lajos Hanzo + 10.1103/253d-s68r + Phys. Rev. Lett. 135, 250804 (2025) + Yanxuan Shao, Jannik L. Wyss, Don Towsley, Adilson E. Motter - Quantum Internet in the Sky: Vision, Challenges, Solutions, and Future Directions - https://arxiv.org/abs/2512.10181 - arXiv:2512.10181v1 Announce Type: new -Abstract: This article envisions the concept of a ``Quantum Internet in the Sky", aiming to establish ubiquitous quantum communication links among distant nodes via free-space optical channels. Our key focus is on deploying quantum communication terminals on non-terrestrial platforms, specifically unmanned aerial vehicles and satellites, at various altitudes. By highlighting the unique characteristics of these platforms compared to terrestrial counterparts, we address inherent challenges and discuss potential solutions through meticulous system designs and analyses of typical non-terrestrial quantum communication scenarios. Finally, we illuminate the path forward by proposing essential future directions that underscore the integration of high-dimensional multipartite quantum communications with sensing, computing, and intelligence for multiple users en route to realizing a fully operational Quantum Internet. - oai:arXiv.org:2512.10181v1 + Deflating quantum error-correcting codes + https://arxiv.org/abs/2512.15887 + arXiv:2512.15887v1 Announce Type: new +Abstract: In this work, we introduce a technique for reducing the length of a quantum stabilizer code, and we call this deflation of the code. Deflation can be seen as a generalization of the well-known puncturing and shortening techniques in cases where more than a single qudit is removed. We show that the parameters of the deflated quantum code can be controlled, and argue that a similar approach is not as beneficial when applied to classical linear codes. Furthermore, it is shown that deflation introduces additional freedom compared to applying just puncturing and shortening consecutively. We exemplify that it is possible to obtain better parameters by deflating a code rather than consecutively using puncturing and shortening. + oai:arXiv.org:2512.15887v1 quant-ph - eess.SP - Fri, 12 Dec 2025 00:00:00 -0500 + cs.IT + math.IT + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - 10.1109/MCOM.003.2300835 - IEEE Communications Magazine, vol. 62, no. 10, pp. 62-68, Oct. 2024 - Phuc V. Trinh, Shinya Sugiura + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Jaron Skovsted Gundersen, Rene B{\o}dker Christensen, Petar Popovski, Rafa{\l} Wisniewski - Optical fuse based on the photorefractive effect for defending the light-injection attacks of quantum key distribution - https://arxiv.org/abs/2512.10205 - arXiv:2512.10205v1 Announce Type: new -Abstract: Light-injection attacks pose critical security threats to quantum key distribution (QKD) systems. Conventional defense methods, such as isolators, filters, and optical power monitoring, are confronted with the threats of specific attacks and the limitations in integration. To address this, we propose and experimentally demonstrate an integrated attack sensing and automatic response unit utilizing the photorefractive effect in a thin-film lithium niobate microring resonator. Our unit provides a high rejection ratio against non-resonant injected light. For resonant attacks exceeding tens of microwatts, the unit can autonomously attenuate the transmission of the quantum signal light, leading to a significant suppression of the secret key rate. This work enhances the security of QKD systems against light-injection attacks by providing a highly sensitive, broadband, and on-chip defense mechanism. - oai:arXiv.org:2512.10205v1 + Quantum Algorithms for Photoreactivity in Cancer-Targeted Photosensitizers + https://arxiv.org/abs/2512.15889 + arXiv:2512.15889v1 Announce Type: new +Abstract: Photodynamic therapy (PDT) is a targeted cancer treatment that uses light-activated photosensitizers to generate reactive oxygen species that selectively destroy tumor cells, generally causing less collateral damage than conventional treatments. However, its clinical success hinges on the availability of photosensitizers with strong optical sensitivity and high efficiency in generating reactive oxygen species. While classical computational methods have provided useful insights into photosensitizer design, they struggle to scale and often lack the accuracy needed for these simulations. In this work, we show how fault-tolerant quantum algorithms can be used to identify promising photosensitizer candidates for PDT. To predict photosensitizer performance, we assess two computational properties. First, we quantify light sensitivity by calculating the cumulative absorption in the therapeutic window with a threshold projection algorithm. Second, we determine the efficiency of reactive oxygen generation by estimating intersystem crossing (ISC) rates using the evolution-proxy approach, complemented by a vibronic dynamic treatment where appropriate. We apply these algorithms to a clinically relevant and actively pursued class of photosensitizers, BODIPY derivatives, including heavy-atom and transition-metal-substituted systems that are challenging for classical methods. Our resource estimates, obtained with PennyLane, suggest that systems with active spaces ranging from 11 to 45 spatial orbitals can be simulated using $180$-$350$ logical qubits and Toffoli gate depths between $10^7$ and $10^9$, placing our algorithms within reach of realistic fault-tolerant quantum devices. This paves the way to an efficient quantum-based workflow for designing photosensitizers that can accelerate the discovery of new PDT agents. + oai:arXiv.org:2512.15889v1 quant-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Min Chen, Hong-Yan Song, Jia-Lin Chen, Peng Ye, Guo-Wei Zhang, Fang-Xiang Wang, Li Zhang, Shuang Wang, De-Yong He, Zhen-qiang Yin, Guang-Can Guo, Wei Chen, Zheng-Fu Han + Yanbing Zhou, Pablo A. M. Casares, Diksha Dhawan, Ignacio Loaiza, Soran Jahangiri, Robert A. Lang, Juan Miguel Arrazola, Stepan Fomichev - Entropic Uncertainty Relations with Quantum Memory in Accelerated Frames via Unruh-DeWitt Detectors - https://arxiv.org/abs/2512.10210 - arXiv:2512.10210v1 Announce Type: new -Abstract: Quantum uncertainty is deeply linked to quantum correlations and relativistic motion. The entropic uncertainty relation with quantum memory offers a powerful way to study how shared entanglement affects measurement precision. However, under acceleration, the Unruh effect can degrade quantum correlations, raising questions about the reliability of QMA-EUR in such settings. Here, we investigate the QMA-EUR for two uniformly accelerating Unruh-DeWitt detectors coupled to a massless scalar field. Using the Kossakowski-Lindblad master equation, we calculate the entropic uncertainty, its lower bound, and the tightness of the relation under different Unruh temperatures. We find that acceleration does not always increase the lower bound on the uncertainty relation. Depending on the initial correlations between the detectors, it may either increase or decrease. This behavior results from the interplay between quantum discord and minimal missing information. Interestingly, a higher quantum discord does not necessarily lead to lower uncertainty. - oai:arXiv.org:2512.10210v1 + Universal and Maximal Entanglement Swapping in General Fermionic Gaussian States + https://arxiv.org/abs/2512.15890 + arXiv:2512.15890v1 Announce Type: new +Abstract: Exploring universal entanglement structure in many-body systems is both fundamental and challenging, particularly when the system undergoes non-unitary operations. In this work, we uncover a universal mechanism for realizing maximal entanglement swapping in fermionic Gaussian states subjected to projective Bell measurements. We consider two initially decoupled, half-filled copies of a free-fermion system in arbitrary dimensions and perform post-selective Bell measurements on half of the corresponding sites across the two copies. Remarkably, the post-measurement state factorizes into a product of Bell pairs, establishing maximal interlayer entanglement entirely independent of the initial Gaussian state. We derive this post-measurement state exactly for general particle-number-conserving fermionic Gaussian states, establishing both the validity and universality of the mechanism, with numerical simulations serving as consistency checks. This phenomenon arises from a robust interplay between fermionic statistics and Gaussianity, revealing a distinct fermionic route to measurement-induced maximal entanglement. + oai:arXiv.org:2512.15890v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.quant-gas + cond-mat.stat-mech + hep-th + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/publicdomain/zero/1.0/ - Ming-Ming Du, Hong-Wei Li, Shu-Ting Shen, Xiao-Jing Yan, Xi-Yun Li, Lan Zhou, Wei Zhong, Yu-Bo Sheng + http://creativecommons.org/licenses/by/4.0/ + Jiyuan Fang, Qicheng Tang, Xueda Wen - Optimal learning of quantum channels in diamond distance - https://arxiv.org/abs/2512.10214 - arXiv:2512.10214v1 Announce Type: new -Abstract: Quantum process tomography, the task of estimating an unknown quantum channel, is a central problem in quantum information theory and a key primitive for characterising noisy quantum devices. A long-standing open question is to determine the optimal number of uses of an unknown channel required to learn it in diamond distance, the standard measure of worst-case distinguishability between quantum processes. Here we show that a quantum channel acting on a $d$-dimensional system can be estimated to accuracy $\varepsilon$ in diamond distance using $O(d^4/\varepsilon^2)$ channel uses. This scaling is essentially optimal, as it matches lower bounds up to logarithmic factors. Our analysis extends to channels with input and output dimensions $d_{\mathrm{in}}$ and $d_{\mathrm{out}}$ and Kraus rank at most $k$, for which $O(d_{\mathrm{in}} d_{\mathrm{out}} k/\varepsilon^2)$ channel uses suffice, interpolating between unitary and fully generic channels. As by-products, we obtain, to the best of our knowledge, the first essentially optimal strategies for operator-norm learning of binary POVMs and isometries, and we recover optimal trace-distance tomography for fixed-rank states. Our approach consists of using the channel only non-adaptively to prepare copies of the Choi state, purify them in parallel, perform sample-optimal pure-state tomography on the purifications, and analyse the resulting estimator directly in diamond distance via its semidefinite-program characterisation. While the sample complexity of state tomography in trace distance is by now well understood, our results finally settle the corresponding problem for quantum channels in diamond distance. - oai:arXiv.org:2512.10214v1 + Closed-Form Optimal Quantum Circuits for Single-Query Identification of Boolean Functions + https://arxiv.org/abs/2512.15901 + arXiv:2512.15901v1 Announce Type: new +Abstract: We study minimum-error identification of an unknown single-bit Boolean function given black-box (oracle) access with one allowed query. Rather than stopping at an abstract optimal measurement, we give a fully constructive solution: an explicit state preparation and an explicit measurement unitary whose computational-basis readout achieves the Helstrom-optimal success probability 3/4 for distinguishing the four possible functions. The resulting circuit is low depth, uses a fixed gate set, and (in this smallest setting) requires no entanglement in the input state. Beyond the specific example, the main message is operational. It highlights a regime in which optimal oracle discrimination is not only well-defined but implementably explicit: the optimal POVM collapses to a compact gate-level primitive that can be compiled, verified, and composed inside larger routines. Motivated by this, we discuss a "what if" question that is open in spirit: for fixed (n,m,k), could optimal k-query identification (possibly for large hypothesis classes) admit deterministic, closed-form descriptions of the inter-query unitaries and the final measurement unitary acting on the natural n+m-qubit input--output registers (and, if needed, small work registers)? Even when such descriptions are not compact and do not evade known circuit-complexity barriers for generic Boolean functions, making the optimum constructive at the circuit level would be valuable for theory-to-hardware translation and for clarifying which forms of "oracle access" are physically meaningful. + oai:arXiv.org:2512.15901v1 quant-ph - cs.CC - cs.DS - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Antonio Anna Mele, Lennart Bittel + http://creativecommons.org/licenses/by/4.0/ + Leonardo Bohac - Generating strong mechanical squeezing via combined squeezed vacuum field and two-tone driving - https://arxiv.org/abs/2512.10215 - arXiv:2512.10215v1 Announce Type: new -Abstract: We propose a novel scheme for generating mechanical squeezed states based on the combined mechanism of a two-tone driving and a squeezed vacuum field. This innovative approach achieves a remarkable improvement in mechanical squeezing performance across the entire range of red/blue detuning ratios. Our study reveals that the squeezed vacuum field not only induces position squeezing of the mechanical oscillator but also facilitates momentum squeezing through phase matching. Moreover, the total squeezing degree exhibits nonlinear enhancement with the increasing of squeezing parameter $r$. The mechanical squeezed state exhibits a $2\pi$-periodic dependence in relation to the squeezing phase $\theta$, offering experimental implementation with a high degree of operational flexibility. Notably, the scheme exhibits strong robustness against cavity dissipation and environmental thermal noise, substantially relaxing the strict parameter-matching requirements inherent in conventional approaches. - oai:arXiv.org:2512.10215v1 + Resource-resolved quantum fluctuation theorems in end-point measurement scheme + https://arxiv.org/abs/2512.15928 + arXiv:2512.15928v1 Announce Type: new +Abstract: Fluctuation theorems provide universal constraints on nonequilibrium energy and entropy fluctuations, making them a natural framework to assess how and to what extent quantum resources become thermodynamically relevant. We develop a unified framework for incorporating a generic quantum resource, including athermality, quantum coherence, and entanglement, into fluctuation theorems. We work within the end point measurement scheme, which avoids an initial energy measurement and allows quantum resources in the initial state to affect nonequilibrium energy statistics. We derive a family of quantum fluctuation theorems, including generalized Jarzynski equalities and Crooks type fluctuation relations, in which corrections decompose into resource resolved contributions. For single systems, we introduce the concept of weight of athermality, and combine it with the weight of coherence to isolate distinct thermodynamic effects of these quantum resources. For bipartite systems, we furthermore obtain two families of entanglement-resolved fluctuation theorems using an appended correlation operator and the best separable approximation, respectively. Finally, we introduce the concepts of coherence and entanglement fluctuation distances, as Kullback Leibler divergences, which quantify the thermodynamic relevance of quantum resources in a process-dependent and operational manner. + oai:arXiv.org:2512.15928v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1002/qute.202500655 - Advanced Quantum Technologies, 2025; e00655 - Xiao-Jie Wu, Huan-Huan Cheng, Cheng-Hua Bai, Shao-Xiong Wu + Sukrut Mondkar, Sayan Mondal, Ujjwal Sen - Integrated Generation and Purification of Entangled Coherent States for Non-Gaussian Teleportation - https://arxiv.org/abs/2512.10225 - arXiv:2512.10225v1 Announce Type: new -Abstract: Entangled coherent states (ECS) provide a powerful non-Gaussian resource for continuous-variable quantum communication, but their generation in scalable architectures remains challenging. We propose an integrated photonic scheme that creates high-fidelity ECS from a two-mode squeezed vacuum via photon subtraction in a symmetric waveguide trimer. The resulting non-Gaussian entanglement is further enhanced by single-photon catalysis, which purifies the distributed state after transmission through lossy channels. Using these purified ECS resources, we analyze a photon-number-based teleportation protocol and demonstrate high-fidelity transfer of both coherent states and Schrodinger cat states. In particular, the teleportation fidelity for cat states exceeds the classical threshold of 2/3 over a broad range of realistic channel and squeezing parameters, whereas Gaussian resources fail to do so. Our results show that integrated photon subtraction and catalysis enable practical, chip-compatible generation of non-Gaussian entanglement suitable for advanced quantum teleportation and continuous-variable quantum networks. - oai:arXiv.org:2512.10225v1 + A Dough-Like Model for Understanding Double-Slit Phenomena + https://arxiv.org/abs/2512.15932 + arXiv:2512.15932v1 Announce Type: new +Abstract: The probabilistic interference fringes observed in the double slit experiment vividly demonstrate the quantum superposition principle, yet they also highlight a fundamental conceptual challenge: the relationship between a system before and after the measurement. According to Copenhagen interpretation, an unobserved quantum system evolves continuously based on the Schrodinger equation, whereas observation induces an instantaneous collapse of the wave function to an eigenstate. This contrast between continuous evolution and sudden collapse renders the single particle behavior particularly enigmatic, especially given that quantum mechanics itself is constructed upon the statistical behavior of ensembles rather than individual entities. In this study, we introduce a Double Slit Diffraction Surrogate Model DSM based on deep learning, designed to capture the mapping between wave functions and probability distributions. The DSM explores multiple potential propagation paths and adaptively selects optimal transmission channels using gradient descent, forming a backbone for the information through the network. By comparing the interpretability of paths and interference, we propose an intuitive physical analogy: the particle behaves like a stretchable dough, extending across both slits, reconnecting after transmission, allowing detachment before the barrier. Monte Carlo simulations confirm that this framework can naturally reproduce the characteristic interference and diffraction probability patterns. Our approach offers a novel, physically interpretable perspective on quantum superposition and measurement induced collapse. The dough analogy is expected to extend to other quantum phenomena. Finally, we provide a dough based picture, attempting to unify interference, entanglement, and tunneling as manifestations of the same underlying phenomenon. + oai:arXiv.org:2512.15932v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Ananga Mohan Datta, William J. Munro, Nicolo Lo Piparo, Kae Nemoto + Ping-Rui Tsai, Tzay-Ming Hong - Catalytic Tomography of Ground States - https://arxiv.org/abs/2512.10247 - arXiv:2512.10247v1 Announce Type: new -Abstract: We introduce a simple protocol for measuring properties of a gapped ground state with essentially no disturbance to the state. The required Hamiltonian evolution time scales inversely with the spectral gap and target precision (up to logarithmic factors), which is optimal. For local observables on geometrically local systems, the protocol only requires Hamiltonian evolution on a quasi-local patch of inverse-gap radius. Our results show that gapped ground states are algorithmically readable from a single copy without a recovery or rewinding procedure, which may drastically reduce tomography overhead in certain quantum simulation tasks. - oai:arXiv.org:2512.10247v1 + AC Stark effect or time-dependent Aharonov-Bohm effect for particle on a ring + https://arxiv.org/abs/2512.15935 + arXiv:2512.15935v1 Announce Type: new +Abstract: We study the effect of a time-varying solenoidal vector potential for a quantum particle confined to a ring. The setup appears to be a time-varying version of the Aharonov-Bohm effect, but since the particle moves in the presence of fields, it is not strictly an Aharonov-Bohm effect. The results are similar to the ac Stark effect, but with a time-varying electric field coming from the vector potential, rather than the scalar potential. We compare and contrast the present effect with the standard ac Stark effect. The signature of this setup is the generation of quasi-energy sidebands which are observable via spectroscopy. + oai:arXiv.org:2512.15935v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + hep-th + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Chi-Fang Chen, Robbie King + 10.1016/j.physleta.2025.131248 + Patrick Hinrichs, Douglas Singleton, Nader Inan - Quantum relaxometry for detecting biomolecular interactions with single NV centers - https://arxiv.org/abs/2512.10269 - arXiv:2512.10269v1 Announce Type: new -Abstract: The investigation of biomolecular interactions at the single-molecule level has emerged as a pivotal research area in life science, particularly through optical, mechanical, and electrochemical approaches. Spins existing widely in biological systems, offer a unique degree of freedom for detecting such interactions. However, most previous studies have been largely confined to ensemble-level detection in the spin degree. Here, we developed a molecular interaction analysis method approaching single-molecule level based on relaxometry using the quantum sensor, nitrogen-vacancy (NV) center in diamond. Experiments utilized an optimized diamond surface functionalized with a polyethylenimine nanogel layer, achieving $\sim$10 nm average protein distance and mitigating interfacial steric hindrance. Then we measured the strong interaction between streptavidin and spin-labeled biotin complexes, as well as the weak interaction between bovine serum albumin and biotin complexes, at both the micrometer scale and nanoscale. For the micrometer-scale measurements using ensemble NV centers, we re-examined the often-neglected fast relaxation component and proposed a relaxation rate evaluation method, substantially enhancing the measurement sensitivity. Furthermore, we achieved nanoscale detection approaching single-molecule level using single NV centers. This methodology holds promise for applications in molecular screening, identification and kinetic studies at the single-molecule level, offering critical insights into molecular function and activity mechanisms. - oai:arXiv.org:2512.10269v1 + Random coding for long-range continuous-variable QKD + https://arxiv.org/abs/2512.15990 + arXiv:2512.15990v1 Announce Type: new +Abstract: Quantum Key Distribution (QKD) schemes are key exchange protocols based on the physical properties of quantum channels. They avoid the computational-hardness assumptions that underlie the security of classical key exchange. Continuous-Variable QKD (CVQKD), in contrast to qubit-based discrete-variable (DV) schemes, makes use of quadrature measurements of the electromagnetic field. CVQKD has the advantage of being compatible with standard telecom equipment, but at long distances has to deal with very low signal to noise ratios, which necessitates labour-intensive error correction. It is challenging to implement the error correction decoding in realtime. + In this paper we introduce a random-codebook error correction method that is suitable for long range Gaussian-modulated CVQKD. We use likelihood ratio scoring with block rejection based on thresholding. For proof-technical reasons, the accept/reject decisions are communicated in encrypted form; in this way we avoid having to deal with non-Gaussian states in the analysis of the leakage. The error correction method is highly parallelisable, which is advantageous for realtime implementation. Under conservative assumptions on the computational resources, we predict a realtime key ratio of at least 8% of the Devetak-Winter value, which outperforms existing reconciliation schemes. + oai:arXiv.org:2512.15990v1 quant-ph - physics.bio-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cs.CR + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1073/pnas.2509102122 - PNAS 122 (35) e2509102122 (2025) - Min Li, Qi Zhang, Xi Kong, Sheng Zhao, Bin-Bin Pan, Ziting Sun, Pei Yu, Zhecheng Wang, Mengqi Wang, Wentao Ji, Fei Kong, Guanglei Cheng, Si Wu, Ya Wang, Sanyou Chen, Xun-Cheng Su, Fazhan Shi + http://creativecommons.org/licenses/by/4.0/ + Arpan Akash Ray, Boris Skoric - Single-molecule Scale Nuclear Magnetic Resonance Spectroscopy using a Robust Near-Infrared Spin Sensor - https://arxiv.org/abs/2512.10278 - arXiv:2512.10278v1 Announce Type: new -Abstract: Nuclear magnetic resonance (NMR) at the single-molecule level with atomic resolution holds transformative potential for structural biology and surface chemistry. Near-surface solid-state spin sensors with optical readout ability offer a promising pathway toward this goal. However, their extreme proximity to target molecules demands exceptional robustness against surface-induced perturbations. Furthermore, life science applications require these sensors to operate in biocompatible spectral ranges that minimize photodamage. In this work, we demonstrate that the PL6 quantum defect in 4H silicon carbide (4H-SiC) can serve as a robust near-infrared spin sensor. This sensor operates at tissue-transparent wavelengths and exhibits exceptional near-surface stability even at depth of 2 nm. Using shallow PL6 centers, we achieve nanoscale NMR detection of proton ($\mathrm{^{1}H}$) spins in immersion oil and fluorine ($\mathrm{^{19}F}$) spins in Fomblin, attaining a detection volume of $\mathrm{(3~nm)^3}$ and a sensitivity reaching the requirement for single-proton spin detection. This work establishes 4H-SiC quantum sensors as a compelling platform for nanoscale magnetic resonance, with promising applications in probing low-dimensional water phases, protein folding dynamics, and molecular interactions. - oai:arXiv.org:2512.10278v1 + Stationary two-qubit entanglement mediated by one-dimensional plasmonic nanoarrays + https://arxiv.org/abs/2512.16016 + arXiv:2512.16016v1 Announce Type: new +Abstract: Entanglement is one of the key measures of quantum correlations present in nanophotonic systems, with promising applications in quantum optics and beyond. Previous studies have shown that the degree of entanglement between two quantum dot qubits is preserved when a metal nanoparticle is used to mediate the interactions between the qubits. In this work, we investigate long-range plasmonic mediation of qubit--qubit entanglement by studying the impact of the number of mediating metal nanoparticles on stationary concurrence. Collinear and periodically spaced metal nanoparticles that satisfy the weak-coupling approximation are considered. An effective model that enables the derivation of the mediated interactions within the framework of cavity quantum electrodynamics is employed. Under weak driving at the single particle resonance frequency, the model shows that odd-number arrays are more robust to entanglement decay. We attribute this to strong inter-qubit dissipative coupling as a result of a hybridized dipole plasmon resonating with the driving frequency in odd-number arrays. These arrays can sustain non-vanishing stationary entanglement beyond an inter-qubit spacing of one micron, opening up the possibility of independent spatial optical probing of each quantum dot. + oai:arXiv.org:2512.16016v1 quant-ph - physics.bio-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yu Chen, Qi Zhang, Yuanhong Teng, Chihang Luo, Zhijie Li, Jinpeng Liu, Ya Wang, Fazhan Shi, Jiangfeng Du + Luke C. Ugwuoke, Tjaart P. J. Kr\"uger, Mark S. Tame - Gradient projection method and stochastic search for some optimal control models with spin chains. II - https://arxiv.org/abs/2512.10290 - arXiv:2512.10290v1 Announce Type: new -Abstract: This article (II) continues the research described in [Morzhin O.V. Gradient projection method and stochastic search for some optimal control models with spin chains. I (submitted)] (Article I), derives the needed finite-dimensional gradients corresponding to the infinite-dimensional gradients obtained in Article I, both for transfer and keeping problems at a certain $N$-dimensional spin chain, and correspondingly adapts a projection-type condition for optimality, gradient projection method (GPM). For the case $N=3$, the given in this article examples together with Example 3 in Article I show that: a) the adapted GPM and genetic algorithm (GA) successfully solved numerically the considered transfer and keeping problems; b) the two- and three-step GPM forms significantly surpass the one-step GPM. Moreover, GA and a special class of controls were successfully used in such the transfer problem that $N=20$ and the final time is not assigned. - oai:arXiv.org:2512.10290v1 + Silicon T centre hyperfine structure and memory protection schemes + https://arxiv.org/abs/2512.16047 + arXiv:2512.16047v1 Announce Type: new +Abstract: Combining the long-coherence of spin qubits and the capability to transmit information and entanglement through photons, spin-photon interfaces (SPIs) are a promising platform for networked quantum computation and long-distance quantum communication. SPIs that possess local `memory' qubits in addition to the optically coupled `communication' qubit can improve remote entanglement fidelities through brokered entanglement schemes and entanglement purification. In these schemes, it is critical to protect the memory qubit from decoherence during entanglement operations on the communications qubit. Silicon, a platform with mature microelectronic and nanophotonic fabrication, is host to the T centre, an SPI with emission in the telecommunications O-band that directly integrates with silicon nanophotonics. Cavity-coupled T centres are a platform for brokered entanglement distribution in silicon photonic circuits and over long-distance optical fibre links. The T centre's electron and nuclear spin qubits are an intrinsic register of communication and memory qubits respectively, with anisotropic hyperfine coupling. In this work we determine the T centre's hydrogen hyperfine coupling tensor. We also introduce schemes to protect against dephasing or eliminate relaxation of the T centre's hydrogen memory qubit during optical excitation. These results address a key challenge for practical T centre quantum networks. + oai:arXiv.org:2512.16047v1 quant-ph - math.OC - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Oleg V. Morzhin + Nicholas Brunelle, Joshua Kanaganayagam, Mehdi Keshavarz, Chloe Clear, Oney Soykal, Myles Ruether, Adam DeAbreu, Amirhossein AlizadehKhaledi, Yihuang Xiong, Nikolay V. Abrosimov, Geoffroy Hautier, Michael Thewalt, Stephanie Simmons, Daniel Higginbottom - Tunable discrete quasi-time crystal from a single drive - https://arxiv.org/abs/2512.10303 - arXiv:2512.10303v1 Announce Type: new -Abstract: The search for exotic temporal orders in quantum matter, such as discrete quasi-time crystals (DQTCs), has become an important theme in nonequilibrium physics. However, realizing these phases has so far required complex protocols, such as drives with multiple incommensurate frequencies. Here, we present a significantly simpler mechanism: the emergence of DQTCs in a dissipative collective spin system subjected to only a single periodic drive. Remarkably, the characteristic frequencies of this novel phase are not fixed but can be continuously tuned by varying the strength of the drive. Even more strikingly, this tunability is punctuated by Arnold tongues, within which the response main frequency locks to rational fractions of the drive. Our model further provides a unified framework that also encompasses stationary, discrete time crystals and chaotic phases. This discovery simplifies the requirements for generating complex temporal orders and opens a viable route towards the experimental control and manipulation of quasi-time crystalline matter. - oai:arXiv.org:2512.10303v1 + Discrete time crystals enhanced by Stark potentials in Rydberg atom arrays + https://arxiv.org/abs/2512.16097 + arXiv:2512.16097v1 Announce Type: new +Abstract: Discrete time crystals (DTCs) are non-equilibrium phases in periodically driven systems that exhibit spontaneous breaking of discrete time-translation symmetry. The stabilization of most DTC phases is achieved via the disorder-induced many-body localization. In this work, we propose an experimental scheme to realize disorder-free DTCs in a periodically driven Rydberg atom array. Our scheme utilizes a linear potential in the atomic detuning to enhance the DTC order, without being tired to (Stark) many-body localization. We numerically demonstrate that the Stark potential enhances the robustness of the DTC against the flip imperfections and extends its lifetime, which are independent of initial states. Thus, our scheme provides a promising way to explore DTCs in Rydberg atom arrays without disorder averaging and special state preparation. + oai:arXiv.org:2512.16097v1 quant-ph + cond-mat.dis-nn cond-mat.quant-gas - physics.atom-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xu Feng, Shuo Liu, Shu Chen, Shi-Xin Zhang + 10.1016/j.physleta.2025.130896 + Physics Letters A 558 (2025) 130896 + Jian-Jia Wang, Ling-Zhi Tang, Yan-Xiong Du, Dan-Wei Zhang - Improved gap dependence in adiabatic state preparation by adaptive schedule - https://arxiv.org/abs/2512.10329 - arXiv:2512.10329v1 Announce Type: new -Abstract: Adiabatic quantum computing is a powerful framework for state preparation, while its evolution time often scales quadratically in the inverse Hamiltonian spectral gap, leading to sub-optimal computational complexity. In this work, we introduce a nonlinear adaptive strategy for finding the time scheduling function, and show that the gap dependence can be quadratically improved to be inverse linear for a wide range of systems under a mild gap measure condition. Through variational analysis, we further demonstrate the optimality of our schedule for systems with linear gap and the partial optimality for general systems, while we also rigorously show that the commonly used linear schedule is never optimal. - oai:arXiv.org:2512.10329v1 + Analyzing the performance of CV-MDI QKD under continuous-mode scenarios + https://arxiv.org/abs/2512.16114 + arXiv:2512.16114v1 Announce Type: new +Abstract: Continuous-variable measurement-device-independent quantum key distribution (CV-MDI QKD) can address vulnerabilities on the detection side of a QKD system. The core of this protocol involves continuous-variable Bell measurements performed by an untrusted third party. However, in high-speed systems, spectrum broadening causes Bell measurements to deviate from the ideal single-mode scenario, resulting in mode mismatches, reduced performance, and compromised security. Here, we introduce temporal modes (TMs) to analyze the performance of CV-MDI QKD under continuous-mode scenarios. The mismatch between Bob's transmitting mode and Bell measurement mode has a more significant effect on system performance compared to that on Alice's side. When the Bell receiver is close to Bob and the mismatch is set to just 5%, the transmission distance drastically decreases from 87.96 km to 18.50 km. In comparison, the same mismatch for Alice reduces the distance to 86.83 km. This greater degradation on Bob's side can be attributed to the asymmetry in the data modification step. Furthermore, the mismatch in TM characteristics leads to a significant reduction in the secret key rate by 83% when the transmission distance is set to 15 km, which severely limits the practical usability of the protocol over specific distances. These results indicate that in scenarios involving continuous-mode interference, such as large-scale MDI network setups, careful consideration of each user's TM characteristics is crucial. Rigorous pre-calibration of these modes is essential to ensure the system's reliability and efficiency. + oai:arXiv.org:2512.16114v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Dong An, Xi Guo + http://creativecommons.org/licenses/by/4.0/ + 10.1103/PhysRevApplied.23.014056 + Physical Review Applied, 23, 014056 (2025) + Yanhao Sun, Ziyang Chen, Xiangyu Wang, Song Yu, Hong Guo - Optomagnonic generation of entangled travelling fields with different polarizations - https://arxiv.org/abs/2512.10338 - arXiv:2512.10338v1 Announce Type: new -Abstract: The optomagnonic coupling between magnons and optical photons is an essential component for building remote quantum networks based on magnonics. Here we show that such a coupling, manifested as the magnon-induced Brillouin light scattering, can be exploited to entangle two propagating optical fields. The protocol employs two pairs of the whispering gallery modes coupled to the same magnon mode in a YIG sphere. In each pair a strong pump field is applied to activate either Stokes or anti-Stokes scattering. Due to the magnon mode involving in the two scattering processes and as a mediation, Stokes and anti-Stokes photons of different polarizations get entangled. The entanglement can be extracted by filtering the travelling output fields centered at the Stokes and anti-Stokes sidebands. Optimal conditions are identified under which strong output entanglement can be achieved. - oai:arXiv.org:2512.10338v1 + Antisymmetrization of composite fermionic states for quantum simulations of nuclear reactions in first-quantization mapping + https://arxiv.org/abs/2512.16138 + arXiv:2512.16138v1 Announce Type: new +Abstract: I present a first-quantization deterministic algorithm for antisymmetrizing a spatially separated target-projectile system containing $N_T$ and $N_p$ identical fermions, respectively. The method constructs a fully antisymmetric wavefunction from the product of two independently antisymmetrized many-body states, each of which may be a superposition of Slater determinants. The algorithm uses a Dicke-state ancilla register that coherently encodes all one-particle exchange channels between the two subsystems, and, crucially, requires only single-particle swaps to generate the full antisymmetric structure. A total of $O(N_T N_p)$ single-particle exchanges are needed, with up to $N_p$ of them implemented in parallel, if an additional $N_p$ ancillae are used. The correct fermionic phase is incorporated through application of $Z$ gates on $N_T$ ancillae, after which the ancilla register is efficiently uncomputed using a compact sequence of controlled operations. This construction provides a nontrivial and scalable protocol for preparing fully antisymmetric states in reaction and scattering simulations, significantly expanding the range of systems that can be addressed with first-quantized quantum algorithms. + oai:arXiv.org:2512.16138v1 quant-ph - cond-mat.mes-hall - physics.app-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + nucl-th + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zi-Xu Lu, Huai-Bing Zhu, Xuan Zuo, Jie Li + http://creativecommons.org/licenses/by/4.0/ + Ionel Stetcu - Generation of mechanical cat-like states via optomagnomechanics - https://arxiv.org/abs/2512.10347 - arXiv:2512.10347v1 Announce Type: new -Abstract: We propose an optomagnomechanical approach for preparing a cat-like superposition state of mechanical motion. Our protocol consists of two steps and is based on the magnomechanical system where the magnetostrictively induced displacement further couples to an optical cavity mode via radiation pressure. We first prepare a squeezed mechanical state by driving the magnomechanical system with a two-tone microwave field. We then switch off the microwave drives and send a weak red-detuned optical pulse to the optical cavity to weakly activate the optomechanical anti-Stokes scattering. We show that $k$ phonons can be subtracted from the prepared squeezed state, conditioned on the detection of $k$ anti-Stokes photons from the cavity output field, which prepares the mechanical motion in a cat-like state. The work provides a new avenue for preparing mechanical superposition states by combining opto- and magnomechanics and may find applications in the study of macroscopic quantum states and the test of collapse theories. - oai:arXiv.org:2512.10347v1 + Tunneling in double-well potentials within stochastic quantization: Application to ammonia inversion + https://arxiv.org/abs/2512.16168 + arXiv:2512.16168v1 Announce Type: new +Abstract: Stochastic quantization - introduced by Nelson in 1966 - describes quantum behavior as a conservative diffusion process in which a particle undergoes Brownian-like motion with a fluctuation amplitude set by Planck's constant. While it fully reproduces conventional quantum mechanics, this approach provides an alternative framework that enables the study of dynamical quantities not easily defined within the standard formulation. In the present work, stochastic quantization is employed to investigate tunneling-time statistics for bound states in double-well potentials. Using first-passage time theory within the stochastic quantization framework, both the mean tunneling time, $\bar{\tau}$, and the full probability distribution, $p({\tau})$, are computed, and the theoretical predictions are validated through extensive numerical simulations of stochastic trajectories for the two potentials considered as representative cases. For the square double-well potential, analytical expressions for $\bar{\tau}$ are derived and show excellent agreement with simulations. In the high-barrier limit, the results reveal a direct relation between the stochastic-mechanical and quantum-mechanical tunneling times, expressed as $\tau_{\mathrm{QM}} = (\pi/2)\bar{\tau}$, where $\tau_{\mathrm{QM}}$ corresponds to half the oscillation period of the probability of finding the particle in either well. This relation is further confirmed for generic double-well systems through a WKB analysis. As a concrete application, the inversion dynamics of the ammonia molecule is analyzed, yielding an inversion frequency of approximately $24$ GHz, in close agreement with experimental observations. These results highlight the potential of stochastic quantization as a powerful and physically insightful framework for analyzing tunneling phenomena in quantum systems. + oai:arXiv.org:2512.16168v1 quant-ph - cond-mat.mes-hall - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hao-Tian Li, Hong-Bin Wang, Zi-Xu Lu, Jie Li + Danilo F. Schafaschek, Giovani L. Vasconcelos, Ant\^onio M. S. Mac\^edo - On the Optimality of a Quantum Key Distribution - https://arxiv.org/abs/2512.10351 - arXiv:2512.10351v1 Announce Type: new -Abstract: Quantum key distribution (QKD) systems require optimal performance of both quantum and classical channels - utilizing as few as possible qubits and bits for establishing as many as possible key bits. Here we report a way to determine if a quantum key distribution model (or protocol) operates in an optimal behavior. This is accomplished by introducing a quantity, called optimality, which is the maximum over the total efficiency of a QKD under any circumstances (any values of QKD parameters). The optimality definition is given for the asymptotic operation of a QKD system - when infinitely many quantum systems are transferred/used in a quantum key distribution protocol or a quantum key distribution system is used infinitely many times. A way to attain the optimality is considered\textemdash implementation of a completely efficient QKD system (a combination of capacity-reaching quantum channel and a completely compressed classical channel) is presented. Optimal versions of BB84-QKD and twin-field QKD are introduced. - oai:arXiv.org:2512.10351v1 + Optimizing Quantum Data Embeddings for Ligand-Based Virtual Screening + https://arxiv.org/abs/2512.16177 + arXiv:2512.16177v1 Announce Type: new +Abstract: Effective molecular representations are essential for ligand-based virtual screening. We investigate how quantum data embedding strategies can improve this task by developing and evaluating a family of quantum-classical hybrid embedding approaches. These approaches combine classical neural networks with parameterized quantum circuits in different ways to generate expressive molecular representations and are assessed across two benchmark datasets of different sizes: the LIT-PCBA and COVID-19 collections. Across multiple biological targets and class-imbalance settings, several quantum and hybrid embedding variants consistently outperform classical baselines, especially in limited-data regimes. These results highlight the potential of optimized quantum data embeddings as data-efficient tools for ligand-based virtual screening. + oai:arXiv.org:2512.16177v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Georgi Bebrov + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Junggu Choi, Tak Hur, Seokhoon Jeong, Kyle L. Jung, Jun Bae Park, Junho Lee, Jae U. Jung, Daniel K. Park - Loophole-free Bell-inequality violation between atomic states in cavity-QED systems mediated by hybrid atom-light entanglement - https://arxiv.org/abs/2512.10378 - arXiv:2512.10378v1 Announce Type: new -Abstract: We present a feasible and scalable approach to testing Bell nonlocality and implementing device-independent quantum key distribution (DI-QKD) between distant atomic states in cavity-based architectures, mediated by hybrid atom-light entanglement. We develop a full theoretical model that incorporates realistic sources of noise -- such as transmission loss, limited light-matter coupling efficiency, and imperfect detection. Our analysis shows that strong Bell-Clauser-Horne-Shimony-Holt (CHSH) violations and secure key generation over tens of kilometers are within reach using current or near-term technology. These results position cavity-based platforms with coherent-state encodings as a promising foundation for future scalable, DI quantum communication networks. - oai:arXiv.org:2512.10378v1 + Entropy Stability and Spectral Concentration under Convex Block Constraints + https://arxiv.org/abs/2512.16192 + arXiv:2512.16192v1 Announce Type: new +Abstract: We investigate entropy minimization problems for quantum states subject to convex block-diagonal constraints. Our principal result is a quantitative stability theorem: if a state has entropy within epsilon of the minimum possible value under a fixed block constraint, then it must lie within O(epsilon^{1/2}) in trace norm of the manifold of entropy minimizers. We show that this rate is optimal. The analysis is entirely finite-dimensional and relies on a precise decomposition of entropy into classical and internal components, together with sharp relative entropy inequalities. As an application, we study finite additive operators whose spectral decomposition induces natural block constraints. In this setting, the stability theorem yields quantitative non-concentration bounds for induced spectral measures. The framework is abstract and independent of arithmetic input. It provides a general stability principle for entropy minimizers under linear spectral constraints. + oai:arXiv.org:2512.16192v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + math.FA + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Pei-Zhe Li, Soumyakanti Bose, Hyunseok Jeong, William J. Munro, Kae Nemoto, Nicol\`o Lo Piparo + Hassan Nasreddine - Quantum Separability Criteria Based on Symmetric Measurements - https://arxiv.org/abs/2512.10380 - arXiv:2512.10380v1 Announce Type: new -Abstract: We propose experimentally feasible separability criteria for bipartite systems based on local symmetric measurements. Through detailed examples, we demonstrate that our criteria can detect entanglement more effectively compared to existing counterparts. Furthermore,we demonstrate the potential for our results to be generalized to general multipartite systems. - oai:arXiv.org:2512.10380v1 + Near-Infrared Quantum Emission from Oxygen-Related Defects in hBN + https://arxiv.org/abs/2512.16197 + arXiv:2512.16197v1 Announce Type: new +Abstract: Color centers hosted in hexagonal boron nitride (hBN) have emerged as a promising platform for single-photon emission and coherent spin-photon interfaces that underpin quantum communication and quantum networking technologies. As a wide-bandgap van der Waals material, hBN can host individual optically active quantum defects emitting across the ultraviolet to visible spectrum, but existing color centers often show broad phonon sidebands (PSBs), unstable emission, or inconvenient wavelengths. Here, we show a simple, scalable oxygen-plasma process that reproducibly creates oxygen-related single quantum emitters in hBN with blinking-free zero-phonon lines spanning the near-infrared (NIR) spectrum from 700-960 nanometers. These emitters demonstrate room-temperature operation, high brightness, and ultra-sharp cryogenic linewidths in the few-gigahertz range under non-resonant excitation. Analysis of the PSBs shows weak electron-phonon coupling and predominant zero-phonon-line emission, while first-principles calculations identify plausible oxygen-related defect configurations. These emitters provide a promising platform for indistinguishable NIR single photons towards free-space quantum networking. + oai:arXiv.org:2512.16197v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/v9gs-6jvz - Phys. Rev. A 112(2025), 062424 - Yu Lu, Wen Zhou, Meng Su, Hong-Xing Wu, Shao-Ming Fei, Zhi-Xi Wang + http://creativecommons.org/licenses/by/4.0/ + Sean Doan, Sahil D. Patel, Yilin Chen, Jordan A. Gusdorff. Mark E. Turiansky, Luis Villagomez, Luka Jevremovic, Nicholas Lewis, Kenji Watanabe, Takashi Taniguchi, Lee C. Bassett, Chris Van de Walle, Galan Moody - Ising on the donut: Regimes of topological quantum error correction from statistical mechanics - https://arxiv.org/abs/2512.10399 - arXiv:2512.10399v1 Announce Type: new -Abstract: Utility-scale quantum computers require quantum error correcting codes with large numbers of physical qubits to achieve sufficiently low logical error rates. The performance of quantum error correction (QEC) is generally predicted through large-scale numerical simulations, used to estimate thresholds, finite-size scaling, and exponential suppression of logical errors below threshold. The connection of QEC to models from statistical mechanics provides an alternative tool for analysing QEC performance. However, predicting the behaviour of these models also requires large-scale numerical simulations, as analytic solutions are not generally known. Here we exploit an exact mapping, from a toric code under bit-flip noise that is post-selected on being syndrome free to the exactly-solvable two-dimensional Ising model on a torus, to derive an analytic solution for the logical failure rate across its full domain of physical error rates. In particular, this mapping provides closed-form expressions for the logical failure rate in four distinct regimes: the path-counting, below-threshold (ordered), near-threshold (critical), and above-threshold (disordered) regimes. Our framework places a number of familiar and long-standing numerical observations on firm theoretical ground. It also motivates explicit ans\"atze for the conventional QEC setting of non-post-selected codes whose statistical mechanics mappings involve random-bond disorder. Specifically, we introduce an effective surface tension model for the below-threshold regime, and a new scaling ansatz for the near-threshold regime, derived from an analysis of the ground state energy cost distribution. By bridging statistical mechanics theory and quantum error correction practice, our results offer a new toolkit for designing, benchmarking, and understanding topological codes beyond current computational limits. - oai:arXiv.org:2512.10399v1 + Amplifying Decoherence-Free Many-Body Interactions with Giant Atoms Coupled to Parametric Waveguide + https://arxiv.org/abs/2512.16232 + arXiv:2512.16232v1 Announce Type: new +Abstract: Parametric amplification offers a powerful means to enhance quantum interactions through field squeezing, yet it typically introduces additional noise which accelerates quantum decoherence, a major obstacle for scalable quantum information processing. The squeezing field is implemented in cavities rather than continuous waveguides, thereby limiting its scalability for applications in quantum simulation. Giant atoms, which couple to waveguides at multiple points, provide a promising route to mitigate dissipation via engineered interference, enabling decoherence-free interactions. We extend the squeezing-amplified interaction to a novel quantum platform combining giant atoms with traveling-wave parametric waveguides based on $\chi^{(2)}$ nonlinearity. By exploiting destructive interference between different coupling points, the interaction between giant atoms is not only significantly enhanced but also becomes immune to squeezed noise. Unlike conventional waveguide quantum electrodynamics without a squeezing pump, the giant emitters exhibit both exchange and pairing interactions, making this platform particularly suitable for simulating many-body quantum physics. More intriguingly, the strengths of these interactions can be smoothly tuned by adjusting the squeezing and coupling parameters. Our architecture thus provides a versatile and scalable platform for quantum simulation of strongly correlated physics and paves the way toward robust quantum control in many-body regimes. + oai:arXiv.org:2512.16232v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Lucas H. English, Sam Roberts, Stephen D. Bartlett, Andrew C. Doherty, Dominic J. Williamson + Xin Wang, Zhao-Min Gao - Robust population transfer by a detuning sign jump: from two-state quantum system to SU(2)-symmetric three-state quantum system - https://arxiv.org/abs/2512.10432 - arXiv:2512.10432v1 Announce Type: new -Abstract: We propose and analyze a robust population-transfer protocol in a driven two-level system based on a sudden sign change of the detuning at the maximum of a smooth coupling pulse. Away from the jump the dynamics is adiabatic, while the sign flip produces a single nonadiabatic kick in the adiabatic basis. Within a simple stepwise adiabatic-sudden approximation we obtain a compact analytic expression for the final transition probability, identify the parameter regimes that yield high-fidelity inversion, and show that the result depends only on the change of the mixing angle across the detuning jump, i.e., solely on the ratio of the peak Rabi frequency to the detuning. Numerical simulations of the full time-dependent Schr\"odinger equation confirm the validity and robustness of this description over a broad parameter range. - We then use the Majorana decomposition to extend the scheme to an SU(2)-symmetric three-state chain driven by the same coupling and detuning functions. In this setting the three-state propagator is expressed in closed form through the two-level Cayley-Klein parameters, which allows us to derive explicit transition probabilities for all three initial states. In particular, we show that for strong coupling the protocol yields almost complete population transfer between the two outer states, with only small transient population of the middle state, while retaining the same intrinsic robustness as in the underlying two-level model. - oai:arXiv.org:2512.10432v1 + Self-testing GHZ state via a Hardy-type paradox + https://arxiv.org/abs/2512.16242 + arXiv:2512.16242v1 Announce Type: new +Abstract: Self-testing is a correlation-based framework that enables the certification of both the underlying quantum state and the implemented measurements without imposing any assumptions on the internal structure of the devices. In this work, we introduce a self-testing protocol for the Greenberger-Horne-Zeilinger (GHZ) state based on a natural generalization of Hardy's nonlocality argument. Within this framework, we prove that the correlation achieving the maximal Hardy success probability constitutes an extremal point of the quantum correlation set and, moreover, that this point is \emph{exposed}. To address experimentally relevant imperfections, we further develop a robust self-testing analysis tailored to the Hardy construction. Additionally, we show that, in this scenario, the quantum correlation that attains the maximal violation of the Hardy-type paradox coincides with the correlation that yields the maximal violation of the Mermin inequality. This establishes a unified perspective in which the same multipartite correlation admits both a logical-paradox interpretation and a Bell-inequality-based characterization. Collectively, our results pave the way for investigating whether the correlations that maximally violate the generalized $N$-party Hardy paradox remain exposed in higher-party regimes. + oai:arXiv.org:2512.16242v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Peter Chernev, Andon A. Rangelov + http://creativecommons.org/licenses/by/4.0/ + Smritikana Patra, Soumyajit Pal, Ranendu Adhikary - Shot and Architecture Adaptive Subspace Variational Quantum Eigensolver for Microwave Simulation - https://arxiv.org/abs/2512.10458 - arXiv:2512.10458v1 Announce Type: new -Abstract: Quantum computing offers a promising paradigm for electromagnetic eigenmode analysis, enabling compact representations of complex field interactions and potential exponential speedup over classical numerical solvers. Recent efforts have applied variational quantum eigensolver (VQE) based methods to compute waveguide modes, demonstrating the feasibility of simulating TE and TM field distributions on noisy intermediate-scale quantum (NISQ) hardware. However, these studies typically employ manually designed, fixed-depth parameterized quantum circuits and uniform measurement-shot strategies, resulting in excessive quantum resource consumption, limited circuit expressivity, and reduced robustness under realistic noise conditions. To address these limitations, we propose an architecture and shot adaptive subspace variational quantum eigensolver for efficient microwave waveguide eigenmode simulation on NISQ devices. The proposed framework integrates a reinforcement learning (RL) based circuit design strategy and an adaptive shot allocation mechanism to jointly reduce quantum resource overhead. Specifically, the RL agent autonomously explores the quantum circuit space to generate hardware-efficient parameterized quantum circuits, while the adaptive measurement scheme allocates sampling resources according to Hamiltonian term weights. Numerical experiments on three- and five-qubit systems demonstrate that the proposed framework achieves accurate estimation of TE and TM mode eigenvalues, with a minimum absolute error down to $10^{-8}$ and reconstructed field distributions under noiseless conditions in excellent agreement with classical electromagnetic solutions. - oai:arXiv.org:2512.10458v1 + Prefix Sums via Kronecker Products + https://arxiv.org/abs/2512.16309 + arXiv:2512.16309v1 Announce Type: new +Abstract: In this work, we revisit prefix sums through the lens of linear algebra. We describe an identity that decomposes triangular all-ones matrices as a sum of two Kronecker products, and apply it to design recursive prefix sum algorithms and circuits. Notably, the proposed family of circuits is the first one that achieves the following three properties simultaneously: (i) zero-deficiency, (ii) constant fan-out per-level, and (iii) depth that is asymptotically strictly smaller than $2\log(n)$ for input length n. As an application, we show how to use these circuits to design quantum adders with $1.893\log(n) + O(1)$ Toffoli depth, $O(n)$ Toffoli gates, and $O(n)$ additional qubits, improving the Toffoli depth and/or Toffoli size of existing constructions. + oai:arXiv.org:2512.16309v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cs.DS + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zhixiu Han, Fanxu Meng, Weidong Li, Xutao Yu, Zaichen Zhang + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Aleksandros Sobczyk, Anastasios Zouzias - Optimal Distributed Similarity Estimation for Unitary Channels - https://arxiv.org/abs/2512.10465 - arXiv:2512.10465v1 Announce Type: new -Abstract: We study distributed similarity estimation for unitary channels (DSEU), the task of estimating the similarity between unitary channels implemented on different quantum devices. We completely address DSEU by showing that, for $n$-qubit unitary channels, the query complexity of DSEU is $\Theta(\sqrt{d})$, where $d=2^n$, for both incoherent and coherent accesses. First, we propose two estimation algorithms for DSEU with these accesses utilizing the randomized measurement toolbox. The query complexities of these algorithms are both $O(\sqrt{d})$. Although incoherent access is generally weaker than coherent access, our incoherent algorithm matches this complexity by leveraging additional shared randomness between devices, highlighting the power of shared randomness in distributed quantum learning. We further establish matching lower bounds, proving that $\Theta(\sqrt{d})$ queries are both necessary and sufficient for DSEU. Finally, we compare our algorithms with independent classical shadow and show that ours have a square-root advantage. Our results provide practical and theoretically optimal tools for quantum devices benchmarking and for distributed quantum learning. - oai:arXiv.org:2512.10465v1 + Feedback Cooling and Thermometry of a Single Trapped Ion Using a Knife Edge + https://arxiv.org/abs/2512.16368 + arXiv:2512.16368v1 Announce Type: new +Abstract: We report on the first feedback cooling of a single trapped ion below the Doppler limit of $\hbar\Gamma/2 k_\mathrm{B}$. The motion of a single ion is monitored in real-time and cooled up to 9-times below the Doppler cooling temperature by applying electronic feedback. Real-time motion detection is implemented by imaging the fluorescence photons emitted by the ion onto a knife edge and detecting the transmitted light, a method used so far to cool trapped nanoparticles. The intensity modulation of the fluorescence resulting from the ion motion is used to generate and apply the feedback signal and also to determine the ion temperature. The method benefits from a high rate of detected scattered photons, which can be a challenge, and which we address by using a parabolic mirror for collecting the fluorescence. + oai:arXiv.org:2512.16368v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.atom-ph + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Congcong Zheng, Kun Wang, Xutao Yu, Ping Xu, Zaichen Zhang + Hans Dang, Sebastian Luff, Martin Fischer, Markus Sondermann, Gerd Leuchs - On Simplest Kochen-Specker Sets - https://arxiv.org/abs/2512.10483 - arXiv:2512.10483v1 Announce Type: new -Abstract: In Phys. Rev. Lett. 135, 190203 (2025) a discovery of the simplest 3D contextual set with 33 vertices, 50 bases, and 14 complete bases is claimed. In this paper, we show that it was previously generated in Quantum 7, 953 (2023) and analyze the meaning, origin, and significance of the simplest contextual sets in any dimension. In particular, we prove that there is no ground to consider the aforementioned set as fundamental since there are many 3D contextual sets with a smaller number of complete bases. We also show that automatic generation of contextual sets from basic vector components automatically yields all known minimal contextual sets of any kind in any dimension and therefore also the aforementioned set in no CPU-time. In the end, we discuss varieties of contextual sets, in particular Kochen-Specker (KS), extended KS, and non-KS sets as well as ambiguities in their definitions. - oai:arXiv.org:2512.10483v1 + Instantaneous velocity during quantum tunnelling + https://arxiv.org/abs/2512.16385 + arXiv:2512.16385v1 Announce Type: new +Abstract: Quantum tunnelling, a hallmark phenomenon of quantum mechanics, allows particles to pass through the classically forbidden region. It underpins fundamental processes ranging from nuclear fusion and photosynthesis to the operation of superconducting qubits. Yet the underlying dynamics of particle motion during tunnelling remain subtle and are still the subject of active debate. Here, by analyzing the temporal evolution of the tunnelling process, we show that the particle velocity inside the barrier continuously relaxes from a large initial value toward a smaller one, and may even approach zero in the evanescent regime. Meanwhile, the probability density within the barrier gradually builds up before reaching its stationary profile, in contrast to existing inherently. In addition, starting from the steady-state equations, we derive an explicit relation between the particle velocity and the barrier width, and show that the velocity in evanescent states approaches zero when the barrier is sufficiently wide. These findings resolve the apparent paradox of a vanishing steady-state velocity coexisting with a finite particle density. We point out that defining an effective speed from the probability density, rather than from the probability current, can lead to spuriously nonzero "stationary speed," as appears to be the case in Ref. [Nature 643, 67 (2025)]. Our work establishes a clear dynamical picture for the formation of tunnelling flow and provides a theoretical foundation for testing time-resolved tunnelling phenomena. + oai:arXiv.org:2512.16385v1 quant-ph - cs.IT - math-ph - math.IT - math.MP - Fri, 12 Dec 2025 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - Mladen Pavicic - - - Chaos, Entanglement and Measurement: Field-Theoretic Perspectives on Quantum Information Dynamics - https://arxiv.org/abs/2512.10484 - arXiv:2512.10484v1 Announce Type: new -Abstract: This work develops tools to understand how quantum information spreads, scrambles, and is reshaped by measurements in many-body systems. First, I study scrambling and pseudorandomness in the Brownian Sachdev-Ye-Kitaev (SYK) model, quantifying pseudorandomness using unitary k-designs and frame potentials. Using Keldysh path integrals with replicas and disorder averaging, I obtain analytic control of the approach to randomness, identify collective modes that delay convergence to Haar-like behavior, and estimate design times as functions of model parameters, clarifying links between scrambling, complexity growth, and random-circuit phenomenology. Second, I construct a field theory for weakly measured SYK clusters. Starting from a system-ancilla description and a continuum monitoring limit, and using fermionic coherent states with replicas and disorder averaging, I derive a nonlinear sigma model that captures measurement back-action and the competition between interaction-induced scrambling and information extraction, predicting characteristic crossover scales and response signatures that distinguish weak monitoring from fully unitary evolution. Third, I develop a strong-disorder renormalization group for measurement-only SYK clusters, based on the SO(2n) replica algebra and Dasgupta-Ma decimation rules. The flow shows features reminiscent of infinite-randomness behavior, but an order-of-limits subtlety renders the leading recursions non-robust, so the analytic evidence for an infinite-randomness fixed point is inconclusive, even though the average second Renyi entropy displays logarithmic scaling. Together, these results provide a unified language to diagnose when many-body dynamics generate operational randomness and how measurements redirect that flow. - oai:arXiv.org:2512.10484v1 - quant-ph - cond-mat.stat-mech - Fri, 12 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Anastasiia Tiutiakina + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Xiao-Wen Shang, Jian-Peng Dou, Feng Lu, Sen Lin, Hao Tang, Xian-Min Jin - The relativistic reason for quantum probability amplitudes - https://arxiv.org/abs/2512.10497 - arXiv:2512.10497v1 Announce Type: new -Abstract: We show that the quantum-mechanical probability distribution involving complex probability amplitudes can be derived from three natural conditions imposed on a relativistically invariant probability function describing the motion of a particle that can take multiple paths simultaneously. The conditions are: (i) pairwise Kolmogorov additivity, (ii) time symmetry, and (iii) Bayes' rule. The resulting solution, parameterized by a single constant, is the squared modulus of a sum of complex exponentials of the relativistic action, thereby recovering the Feynman path-integral formulation of quantum mechanics. - oai:arXiv.org:2512.10497v1 + Coined Quantum Walks on Complex Networks for Quantum Computers + https://arxiv.org/abs/2512.16400 + arXiv:2512.16400v1 Announce Type: new +Abstract: We propose a quantum circuit design for implementing coined quantum walks on complex networks. In complex networks, the coin and shift operators depend on the varying degrees of the nodes, which makes circuit construction more challenging than for regular graphs. To address this issue, we use a dual-register encoding. This approach enables a simplified shift operator and reduces the resource overhead compared to previous methods. We implement the circuit using Qmod, a high-level quantum programming language, and evaluated the performance through numerical simulations on Erd\H{o}s-R\'enyi, Watts-Strogatz, and Barab\'asi-Albert models. The results show that the circuit depth scales as approximately $N^{1.9}$ regardless of the network topology. Furthermore, we execute the proposed circuits on the ibm\_torino superconducting quantum processor for Watts-Strogatz models with $N=4$ and $N=8$. The experiments show that hardware-aware optimization slightly improved the $L_1$ distance for the larger graph, whereas connectivity constraints imposed overhead for the smaller one. These results indicate that while current NISQ devices are limited to small-scale validations, the polynomial scaling of our framework makes it suitable for larger-scale implementations in the early fault-tolerant quantum computing era. + oai:arXiv.org:2512.16400v1 quant-ph - gr-qc - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Karol Sajnok, Kacper D\k{e}bski, Andrzej Dragan + Rei Sato - Tianyan: Cloud services with quantum advantage - https://arxiv.org/abs/2512.10504 - arXiv:2512.10504v1 Announce Type: new -Abstract: Tianyan Quantum Cloud Platform offers cloud services demonstrating quantum advantage capabilities with a Zuchongzhi 3.0-like superconducting quantum processor. This cloud-accessible superconducting quantum prototype, named Tianyan-287, features 105 qubits and achieves high operational fidelities, with single-qubit gates, two-qubit gates, and readout fidelity at 99.90%, 99.56%, 98.7%, respectively. For a specific benchmark task involving random circuit sampling on a 74-qubit system over 24 cycles, the platform completes one million samples in just 18.4 minutes. In contrast, state-of-the-art classical supercomputers would require approximately 16,000 years to complete the equivalent calculation. To facilitate this, the platform provides access via Cqlib, an open-source SDK designed for working with quantum systems at the level of extended quantum circuits, operators, and primitives. The cloud service aims to democratize access to high-performance quantum hardware, enabling the community to validate and explore practical quantum advantages. - oai:arXiv.org:2512.10504v1 + Quantum-Inspired Ising Machines for Quantum Chemistry Calculations + https://arxiv.org/abs/2512.16435 + arXiv:2512.16435v1 Announce Type: new +Abstract: Four decades after Richard Feynman's famous remark, we have reached a stage at which nature can be simulated quantum mechanically. Quantum simulation is among the most promising applications of quantum computing. However, like many quantum algorithms, it is severely constrained by noise in near-term hardware. Quantum-inspired algorithms provide an attractive alternative by avoiding the need for error-prone quantum devices. In this study, we demonstrate that the coherent Ising machine and simulated bifurcation algorithms can accurately reproduce the electronic energy profiles of H_2 and H_2O, capturing their essential energetic features. Notably, we obtain computational times of 1.2 s and 2.4 s for the H_2 and H_2O profiles, respectively, representing a substantial speed-up compared to gate-based quantum computing approaches, which typically require at least 6 s to compute a single molecular geometry with comparable accuracy. These results highlight the potential of quantum-inspired approaches for scaling to larger molecular systems and for future applications in chemistry and materials science. + oai:arXiv.org:2512.16435v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Tianyan Quantum Group + http://creativecommons.org/licenses/by/4.0/ + Mahmood Hasani, Hadis Salasi, Negar Ashari Astani - Encoding parameters by measurement: Forgetting can be better in quantum metrology - https://arxiv.org/abs/2512.10541 - arXiv:2512.10541v1 Announce Type: new -Abstract: We introduce quantum parameter estimation with the encoding being via a quantum measurement. We quantify the precision for estimating parameters characterizing a general two-outcome qubit measurement, considering two cases: when the outcomes of the encoding measurement are recorded and when the same are ignored. We find that in a large variety of such estimation scenarios, forgetting the outcomes yields higher precision. We derive a necessary criterion under which remembering the measurement outcomes provides better precision in comparison to the outcome-forgotten strategy. Furthermore, we establish a necessary and sufficient criterion for the simultaneous estimation of two parameters encoded by an arbitrary quantum process, including those involving measurements, using qubit probes, and find when the quantum Cram\'er$-$Rao bound is valid and achievable. For simultaneous estimation of two parameters characterizing the measurement, we find that the achievable quantum Cram\'er$-$Rao bound can be a valid precision bound only when the measurement direction depends on the parameters of interest. - oai:arXiv.org:2512.10541v1 + Classical and quantum electromagnetic momentum in anisotropic optical waveguides + https://arxiv.org/abs/2512.16495 + arXiv:2512.16495v1 Announce Type: new +Abstract: The guided modes supported by dielectric channel waveguides act as individual carriers of momentum. We show this by proving that the modes satisfy an orthogonality condition which relates to the momentum of the optical electromagnetic field, with a link to the more familiar power (energy) orthogonality. This result forms the basis for a rigorous, self-consistent procedure for the quantization of broadband guided electromagnetic fields in the typical channels used in integrated photonic circuits. Our work removes the existing theoretical gap between the classical solution of the Maxwell equations for guided fields and the intuitive understanding of photons in waveguides. The presented approach is valid for straight, lossless, and potentially anisotropic, dielectric waveguides of general shape, in the linear regime, and including material dispersion. Examples for the hybrid modes of a thin film lithium niobate strip waveguide are briefly discussed. + oai:arXiv.org:2512.16495v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Shuva Mondal, Priya Ghosh, Ujjwal Sen + Denis Kopylov, Manfred Hammer - Hybrid Quantum Annealing Approach for High-Dimensional and Multi-Criteria Constrained Quadratic Optimization in Arctic Ship Routing - https://arxiv.org/abs/2512.10544 - arXiv:2512.10544v1 Announce Type: new -Abstract: The opening of Arctic sea routes presents unprecedented opportunities for global trade but poses significant operational and computational challenges due to the dynamic nature of sea ice conditions. This study formulates a multi criteria Arctic route optimization problem that integrates Copernicus Marine Environment Monitoring Service (CMEMS) variables into a Constrained Quadratic Model (CQM) and solves it using D Wave's hybrid quantum classical solver. We benchmark the feasibility and scalability of this approach against classical Mixed Integer Quadratic Programming (MIQP) solvers such as Gurobi and CPLEX. Results show that the CQM formulation achieves feasible solutions with stable runtimes as quadratic density increases, demonstrating 10 to 100 times faster convergence and reduced computational time compared with classical solvers, while also improving route smoothness by approximately 10 percent and reducing total length by approximately 1 percent. This reflects the effectiveness of the hybrid quantum annealing approach for Arctic routing problems. - oai:arXiv.org:2512.10544v1 + Replica Keldysh field theory of quantum-jump processes: General formalism and application to imbalanced and inefficient fermion counting + https://arxiv.org/abs/2512.16520 + arXiv:2512.16520v1 Announce Type: new +Abstract: Measurement-induced phase transitions have largely been explored for projective or continuous measurements of Hermitian observables, assuming perfect detection without information loss. Yet such transitions also arise in more general settings, including quantum-jump processes with non-Hermitian jump operators, and under inefficient detection. A theoretical framework for treating these broader scenarios has been missing. Here we develop a comprehensive replica Keldysh field theory for general quantum-jump processes in both bosonic and fermionic systems. Our formalism provides a unified description of pure-state quantum trajectories under efficient detection and mixed-state dynamics emerging from inefficient monitoring, with deterministic Lindbladian evolution appearing as a limiting case. It thus establishes a direct connection between phase transitions in nonequilibrium steady states of driven open quantum matter and in measurement-induced dynamics. As an application, we study imbalanced and inefficient fermion counting in a one-dimensional lattice system: monitored gain and loss of fermions occurring at different rates, with a fraction of gain and loss jumps undetected. For imbalanced but efficient counting, we recover the qualitative picture of the balanced case: entanglement obeys an area law for any nonzero jump rate, with an extended quantum-critical regime emerging between two parametrically separated length scales. Inefficient detection introduces a finite correlation length beyond which entanglement, as quantified by the fermionic logarithmic negativity, obeys an area law, while the subsystem entropy shows volume-law scaling. Numerical simulations support our analytical findings. Our results offer a general and versatile theoretical foundation for studying measurement-induced phenomena across a wide class of monitored and open quantum systems. + oai:arXiv.org:2512.16520v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Tara Kit, Kimsay Pov, Myeongseong Go, Leanghok Hour, Arim Ryou, Kiwoong Kim, Tae-Kyung Kim, Youngsun Han + Felix Kloiber-Tollinger, Lukas M. Sieberer - Sensitivity threshold defines the optimal spin subset for ensemble quantum sensing - https://arxiv.org/abs/2512.10549 - arXiv:2512.10549v1 Announce Type: new -Abstract: Finite drive power leaves unavoidable spatial gradients in control fields, preventing spin ensembles from reaching the standard-quantum-limit sensitivity. We derive an analytic expression of ensemble sensitivity for inhomogeneous spin sensors and introduce sensitivity thresholds that reveal the optimal spin subset. Applied to both pulsed and continuous-wave magnetometry, the optimal subsets deliver up to a tenfold improvement over conventional schemes relying on nominally uniform regions of the ensembles. We demonstrate phase-only digital holography to implement the optimal subsets and show that residual aberrations add less than 1 dB of sensitivity loss. Our framework imposes no fundamental trade-offs and extends quantum sensing to heterogeneous sensing environments. - oai:arXiv.org:2512.10549v1 + Wichmann-Kroll vacuum polarization density in a finite Gaussian basis set + https://arxiv.org/abs/2512.16569 + arXiv:2512.16569v1 Announce Type: new +Abstract: This work further develops the calculation of QED effects in a finite Gaussian basis. We focus on the non-linear ${\alpha}(Z{\alpha})^{n\ge 3}$ contribution to the vacuum polarization density, computing the energy shift of 1s$_{1/2}$ states of hydrogen-like ions. Our goal is to improve the numerical computations to achieve a precision comparable to that of Green's function methods reported in the literature. To do so, an analytic expression for the linear contribution to the vacuum polarization density is derived using Riesz projectors. Alternative formulations of the vacuum polarization density and their relation is discussed. The convergence of the finite Gaussian basis scheme is investigated, and the numerical difficulties that arise are characterized. In particular, an error analysis is performed to assess the method's robustness to numerical noise. We then report a strategy for computing the energy shift with sufficient precision to enable a sensible extrapolation of the partial-wave expansion. A key feature of the procedure is the use of even-tempered basis sets, allowing for an extrapolation towards the complete basis set limit. + oai:arXiv.org:2512.16569v1 quant-ph - physics.app-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Suwan I. Kang, Minhyeok Kim, Sanghyo Park, Heonsik Lee, Keunyoung Lee, Donggyu Kim + Ryan Benazzouk, Maen Salman, Trond Saue - Quantum-Amplified M/G/1/K Simulation: A Comparator-Controlled Framework for Arbitrary Service Distributions - https://arxiv.org/abs/2512.10558 - arXiv:2512.10558v1 Announce Type: new -Abstract: Finite-capacity single-server queues with general service-time distributions form the backbone of numerous real-world systems, yet classical simulation of performance metrics such as blocking probabilities and delay becomes computationally prohibitive as service variability or required precision increases. This work presents the first coherent quantum circuit for simulating an M/G/1/K queue under arbitrary service-time laws. The circuit encodes the service distribution through a logarithmic-depth ladder of $R_y$ rotations and enforces buffer constraints via a comparator-controlled phase gate, while preserving the quadratic speed-up of amplitude amplification. Grover iterations center on estimating the expected number of customers in the system, yielding provable $O(\sqrt{N})$ variance reduction and closed-form confidence bounds, where $N$ denotes the number of shots. Empirical evaluations on IBM quantum simulators across four service distributions and three traffic intensities demonstrate fidelity above 0.99 with four qubits and above 0.76 with ten qubits, with Jensen-Shannon divergence below 0.11. Waiting-time estimation errors decrease by an order of magnitude as system load approaches capacity and remain within 3% in high-traffic regimes using registers of up to 63 qubits. These results establish the first end-to-end quantum simulation framework for finite-buffer, non-Markovian queueing systems and provide a concrete foundation for quantum-accelerated performance analysis in service-oriented architectures. - oai:arXiv.org:2512.10558v1 + The measured speed in the evanescent regime reflects the spatial decay of the wavefunction, not particle motion + https://arxiv.org/abs/2512.16580 + arXiv:2512.16580v1 Announce Type: new +Abstract: The recent paper by Sharoglazova et al. reports an energy-dependent parameter $\nu$ extracted from the spatial distribution of photons in a coupled-waveguide experiment. The authors interpret $\nu$ as the speed of quantum particles, even in the classically forbidden regime, and claim that its finite value contradicts the Bohmian mechanics prediction of zero particle velocity. This challenge arises from a fundamental misunderstanding of the operational meaning of v within the Bohmian ontological framework. We demonstrate that v quantifies the spatial gradient of the wavefunctions amplitude, a geometric property of the guiding field, not the kinematical velocity of point-like particles. The experiment therefore does not challenge but rather illustrates the clean ontological separation between the wave and particle aspects inherent to Bohmian mechanics. + oai:arXiv.org:2512.16580v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Or Peretz, Michal Koren, Nir Perel + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Weixiang Ye - Insensitivity points and performance of open quantum interferometers under number- conserving & non-conserving Lindblad dynamics - https://arxiv.org/abs/2512.10559 - arXiv:2512.10559v1 Announce Type: new -Abstract: We investigate the phase sensitivity of a linear two-mode atom interferometer subject to environmental noise, modeled within the framework of open quantum systems with both number- conserving and non-conserving Lindblad operators. Considering several input states, we first study the cases N=1,2 (N number of particles) and perform numerical simulations for N>2. The sensitivity as a function of the holding time can display divergence points where phase estimation becomes impossible, to which we refer as insensitivity points. We characterize their behavior as the input state, particle number, and noise operator are varied, and we find that their positions are independent of the noise intensity. Moreover, while our fixed measurement scheme may favor number-conserving noise at small N (i.e., having better sensitivity), the Cram\'er-Rao bound reveals that particle non-conserving noise yields strictly lower achievable sensitivity for all particle numbers. - oai:arXiv.org:2512.10559v1 + Giant-atom quantum acoustodynamics in hybrid superconducting-phononic integrated circuits + https://arxiv.org/abs/2512.16582 + arXiv:2512.16582v1 Announce Type: new +Abstract: We demonstrate a giant atom by coupling a superconducting transmon qubit to a lithium niobate phononic waveguide at two points separated by about 600 acoustic wavelengths, with a propagation delay of 125 ns. The giant atom yields non-Markovian relaxation dynamics characterized by phonon backflow and a frequency-dependent effective decay rate varying four-fold over merely 4 MHz, corresponding to a Purcell factor exceeding 40. Exploiting this frequency-dependent dissipation, we prepare quantum superposition states with high purity. Our results establish phononic integrated circuits as a versatile platform for giant-atom physics, providing highly tunable quantum devices for advanced quantum information processing. + oai:arXiv.org:2512.16582v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Tommaso Favalli, \v{Z}an Kokalj, Andrea Trombettoni + Lintao Xiao, Bo Zhang, Yu Zeng, Xiaoxuan Pan, Jia-Qi Wang, Ziyue Hua, Hongwei Huang, Yifang Xu, Guangming Xue, Haifeng Yu, Xin-Biao Xu, Weiting Wang, Chang-Ling Zou, Luyan Sun - Topology-Guided Quantum GANs for Constrained Graph Generation - https://arxiv.org/abs/2512.10582 - arXiv:2512.10582v1 Announce Type: new -Abstract: Quantum computing (QC) promises theoretical advantages, benefiting computational problems that would not be efficiently classically simulatable. However, much of this theoretical speedup depends on the quantum circuit design solving the problem. We argue that QC literature has yet to explore more domain specific ansatz-topologies, instead of relying on generic, one-size-fits-all architectures. In this work, we show that incorporating task-specific inductive biases -- specifically geometric priors -- into quantum circuit design can enhance the performance of hybrid Quantum Generative Adversarial Networks (QuGANs) on the task of generating geometrically constrained K4 graphs. We evaluate a portfolio of entanglement topologies and loss-function designs to assess their impact on both statistical fidelity and compliance with geometric constraints, including the Triangle and Ptolemaic inequalities. Our results show that aligning circuit topology with the underlying problem structure yields substantial benefits: the Triangle-topology QuGAN achieves the highest geometric validity among quantum models and matches the performance of classical Generative Adversarial Networks (GAN). Additionally, we showcase how specific architectural choices, such as entangling gate types, variance regularization and output-scaling govern the trade-off between geometric consistency and distributional accuracy, thus emphasizing the value of structured, task-aware quantum ansatz-topologies. - oai:arXiv.org:2512.10582v1 + Indistinguishable photons from a two-photon cascade + https://arxiv.org/abs/2512.16617 + arXiv:2512.16617v1 Announce Type: new +Abstract: Decay of a four-level diamond scheme via a cascade is a potential source of entangled photon pairs. A solid-state implementation is the biexciton cascade in a semiconductor quantum dot. While high entanglement fidelities have been demonstrated, the two photons, XX and X, are temporally correlated, typically resulting in poor photon coherence. Here, we demonstrate a high two-photon interference visibility (a measure of the photon coherence) for both XX (V=94$\pm$2%) and X (V=82$\pm$6%) photons. This is achieved by Purcell-enhancing the biexciton transition in a low-noise device. We find that the photon coherence follows the well-known quantum optics result upon tuning the XX:X lifetime ratio over two orders of magnitude. + oai:arXiv.org:2512.16617v1 quant-ph - cs.LG - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Tobias Rohe, Markus Baumann, Michael Poppel, Gerhard Stenzel, Maximilian Zorn, Claudia Linnhoff-Popien + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Timon L. Baltisberger, Francesco Salusti, Mark R. Hogg, Malwina A. Marczak, Nils Heinisch, Sascha R. Valentin, Stefan Schumacher, Arne Ludwig, Klaus D. J\"ons, Richard J. Warburton - Efficient simulation of low-entanglement bosonic Gaussian states in polynomial time - https://arxiv.org/abs/2512.10643 - arXiv:2512.10643v1 Announce Type: new -Abstract: Bosonic Gaussian states appear ubiquitously in quantum optics and condensed matter physics but remain difficult to simulate classically due to the hafnian bottleneck. We present an efficient algorithm that converts pure bosonic Gaussian states into matrix product states (MPSs), with a computational cost governed solely by the entanglement and not by the number of bosonic modes. Our method combines a Gaussian singular value decomposition with a projected-creation-operator mapping that constructs local MPS tensors without computing hafnians. Benchmarking on covariance matrices from the Jiuzhang 2.0 and Jiuzhang 4.0 Gaussian boson sampling experiments demonstrates substantial speedups over previous tensor-network approaches in the low-entanglement regime relevant to lossy devices. The method provides a scalable classical simulation framework for bosonic Gaussian states with limited entanglement and extends the applicability of MPS-based methods to a broad range of bosonic systems. - oai:arXiv.org:2512.10643v1 + Fast Native Three-Qubit Gates and Fault-Tolerant Quantum Error Correction with Trapped Rydberg Ions + https://arxiv.org/abs/2512.16641 + arXiv:2512.16641v1 Announce Type: new +Abstract: Trapped ions as one of the most promising quantum-information-processing platforms, yet conventional entangling gates mediated by collective motion remain slow and difficult to scale. Exciting trapped ions to high-lying electronic Rydberg states provides a promising route to overcome these limitations by enabling strong, long-range dipole-dipole interactions that support much faster multi-qubit operations. Here, we introduce the first scheme for implementing a native controlled-controlled-Z gate with microwave-dressed Rydberg ions by optimizing a single-pulse protocol that accounts for the finite Rydberg-state lifetime. The resulting gate outperforms standard decompositions into one- and two-qubit gates by achieving fidelities above 97% under realistic conditions, with execution times of about 2 microseconds at cryogenic temperatures. To explore the potential of trapped Rydberg ions for fault-tolerant quantum error correction, and to illustrate the utility of three-qubit Rydberg-ion gates in this context, we develop and analyze a proposal for fault-tolerant, measurement-free quantum error correction using the nine-qubit Bacon-Shor code. Our simulations confirm that quantum error correction can be performed in a fully fault-tolerant manner on a linear Rydberg-ion chain despite its limited qubit connectivity. These results establish native multiqubit Rydberg-ion gates as a valuable resource for fast, high-fidelity quantum computing and highlight their potential for fault-tolerant quantum error correction. + oai:arXiv.org:2512.16641v1 quant-ph - cond-mat.str-el - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Tong Liu, Hui-Ke Jin, Tao Xiang, Hong-Hao Tu + Katrin Bolsmann, Thiago L. M. Guedes, Weibin Li, Joseph W. P. Wilkinson, Igor Lesanovsky, Markus M\"uller - All-photonic entanglement swapping with remote quantum dots - https://arxiv.org/abs/2512.10651 - arXiv:2512.10651v1 Announce Type: new -Abstract: Entanglement swapping is a protocol that details how to create entanglement between previously uncorrelated particles. Its all-photonic version - mediated by the interference of photon pairs generated by separate quantum systems-finds disparate applications in quantum networks. So far, all-photonic entanglement swapping between remote systems has been implemented only using sources that operate probabilistically. However, the scaling up of quantum networks requires deterministic quantum emitters that do not suffer from a trade-off between degree of entanglement and photonpair generation rate. Here, we demonstrate all-photonic entanglement swapping using photon-pairs generated by two separate GaAs quantum dots. The emitters are deterministically embedded in hybrid semiconductor-piezoelectric devices that make the entangled-photons from two dissimilar quantum dots nearly identical. Entanglement swapping is demonstrated with a fidelity as high as 0.71(2), more than 10 standard deviations above the classical limit. The experimental data are quantitatively explained by a theoretical model that also suggests how to boost the protocol performances. Our work opens the path to the exploitation of quantum dot entangled-photon sources in quantum repeater networks. - oai:arXiv.org:2512.10651v1 + Scalable tests of quantum contextuality from stabilizer-testing nonlocal games + https://arxiv.org/abs/2512.16654 + arXiv:2512.16654v1 Announce Type: new +Abstract: Soon after the dawn of quantum error correction, DiVincenzo and Peres observed that stabilizer codewords could give rise to simple proofs of quantumness via contextuality. This discovery can be recast in the language of nonlocal games: every $n$-qubit stabilizer state defines a specific "stabilizer-testing" $n$-player nonlocal game, which quantum players can win with probability one. If quantum players can moreover outperform all possible classical players, then the state is contextual. However, the classical values of stabilizer-testing games are largely unknown for scalable examples beyond the $n$-qubit GHZ state. We introduce several new methods for upper-bounding the classical values of these games. We first prove a general coding-theory bound for all stabilizer-testing games: if the classical value $p_{\mathrm{cl}}^* < 1$, then $p_{\mathrm{cl}}^* \leq 7/8$, i.e., there is no classical strategy that can perform as well as the optimal quantum strategy even in an asymptotic sense. We then show how to tighten this bound for the most common scalable examples, namely GHZ, toric-code and cyclic cluster states. In particular, we establish an asymptotically tight upper bound for cyclic cluster states using transfer-matrix methods. This leads to the striking conclusion that measuring an exponentially small fidelity to the cyclic cluster state will suffice to witness its contextuality. + oai:arXiv.org:2512.16654v1 quant-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + cond-mat.str-el + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Mattia Beccaceci, Giuseppe Ronco, Fabrizio Cienzo, Pierpaolo Bassetti, Alessandro Laneve, Francesco Basso Basset, Tobias M. Krieger, Qurin Buchinger, Francesco Salusti, Barbara Souza Damasceno, Silke Kuhn, Saimon F. Covre da Silva, Sandra Stroj, Klaus D. J\"ons, Sven H\"ofling, Tobias Huber-Loyola, Armando Rastelli, Michele B. Rota, Rinaldo Trotta + Wanbing Zhao, H. W. Shawn Liew, Wen Wei Ho, Chunxiao Liu, Vir B. Bulchandani - Pulsed learning for quantum data re-uploading models - https://arxiv.org/abs/2512.10670 - arXiv:2512.10670v1 Announce Type: new -Abstract: While Quantum Machine Learning (QML) holds great potential, its practical realization on Noisy Intermediate-Scale Quantum (NISQ) hardware has been hindered by the limitations of variational quantum circuits (VQCs). Recent evidence suggests that VQCs suffer from severe trainability and noise-related issues, leading to growing skepticism about their long-term viability. However, the possibility of implementing learning models directly at the pulse-control level remains comparatively unexplored and could offer a promising alternative. In this work, we formulate a pulse-based variant of data re-uploading, embedding trainable parameters directly into the native system's dynamics. We benchmark our approach on a simulated superconducting transmon processor with realistic noise profiles. The pulse-based model consistently outperforms its gate-based counterpart, exhibiting higher test accuracy and improved generalization under equivalent noise conditions. Moreover, by systematically increasing noise strength, we show that pulse-level implementations retain higher fidelity for longer, demonstrating enhanced resilience to decoherence and control errors. These results suggest that pulse-native architectures, though less explored, may offer a viable and hardware-aligned path forward for practical QML in the NISQ era. - oai:arXiv.org:2512.10670v1 + Shaping Dynamics Through Memory: A Study of Reservoir Profiles in Open Quantum Systems + https://arxiv.org/abs/2512.16657 + arXiv:2512.16657v1 Announce Type: new +Abstract: In this work, we investigate how different reservoir memory profiles influence the dynamical evolution of a single waveguide coupled to an external environment. We compare three representative memory kernels: Lorentzian, Gaussian and Uniform, highlighting their distinct spatial correlations and their impact on system behavior. We compute the transmission amplitude, transparency properties, as well as long-time behavior of the system under each memory model. To quantify deviations from Markovian dynamics, we employ a non-Markovianity measure based on information backflow, allowing a direct comparison between the structured reservoirs and the Markovian limit. Our results reveal clear signatures of memoryless-induced modifications in the transmission spectrum and demonstrate how specific reservoir profiles enhance or suppress non-Markovian effects. + oai:arXiv.org:2512.16657v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Ignacio B. Acedo, Pablo Rodriguez-Grasa, Pablo Garcia-Azorin, Javier Gonzalez-Conde + J. R. Silva, C. Antunis B. S. Santos - A Cryogenic Muon Tagging System Based on Kinetic Inductance Detectors for Superconducting Quantum Processors - https://arxiv.org/abs/2512.10679 - arXiv:2512.10679v1 Announce Type: new -Abstract: Ionizing radiation has emerged as a potential limiting factor for superconducting quantum processors, inducing quasiparticle bursts and correlated errors that challenge fault-tolerant operation. Atmospheric muons are particularly problematic due to their high energy and penetration power, making passive shielding ineffective. Therefore, monitoring the real-time muon flux is crucial to guide the development of alternative error-correction or protection strategies. We present the design, simulation, and first operation of a cryogenic muon-tagging system based on Kinetic Inductance Detectors (KIDs) for integration with superconducting quantum processors. The system consists of two KIDs arranged in a vertical stack and operated at ~20 mK. Monte Carlo simulations based on Geant4 guided the prototype design and provided reference expectations for muon-tagging efficiency and accidental coincidences due to ambient $\gamma$-rays. We measured a muon-induced coincidence rate among the top and bottom detectors of (192 $\pm$ 9) $\times$ 10$^{-3}$ events/s, in excellent agreement with the Monte Carlo prediction. The prototype achieves a muon-tagging efficiency of about 90% with negligible dead time. These results demonstrate the feasibility of operating a muon-tagging system at millikelvin temperatures and open the path toward its integration with multi-qubit chips to veto or correct muon-induced errors in real time. - oai:arXiv.org:2512.10679v1 + Topological magic response in quantum spin chains + https://arxiv.org/abs/2512.16673 + arXiv:2512.16673v1 Announce Type: new +Abstract: Topological matter provides natural platforms for robust, non-local information storage, central to quantum error correction. Yet, while the relation between entanglement and topology is well established, little is known about the role of nonstabilizerness (or magic), a pivotal concept in fault-tolerant quantum computation, in topological phases. We introduce the concept of topological magic response, the ability of a state to spread over stabilizer space when perturbed by finite-depth non-Clifford circuits. Unlike a topological invariant or order parameter, this response function probes how a phase reacts to non-Clifford perturbations, revealing the presence of non-local quantum correlations. In Ising-type spin chains, we show that symmetry-broken and paramagnetic phases lack such a response, whereas symmetry-protected topological (SPT) phases always display it. To capture this, we utilize a combination of stabilizer R\'{e}nyi entropies that, in analogy with topological entanglement entropy, isolates non-locally stored information. Using exact analytic computations and matrix product states simulations based on an algorithmic technique we introduce, we show that SPT phases doped with $T$ gates support robust topological magic response, while trivial phases remain featureless. + oai:arXiv.org:2512.16673v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Ambra Mariani, Laura Cardani, Mustafa Bal, Nicola Casali, Ivan Colantoni, Angelo Cruciani, Giorgio Del Castello, Daniele Delicato, Francesco De Dominicis, Matteo del Gallo Raccagiovine, Matteo Folcarelli, Sabrina Garattoni, Anna Grassellino, Mehmood Khan Yasir Raja, Valerio Pettinacci, Alberto Ressa, Tanay Roy, Marco Vignati, David v Zanten + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Ritu Nehra, Poetri Sonya Tarabunga, Martina Frau, Mario Collura, Emanuele Tirrito, Marcello Dalmonte - Advantage in distributed quantum computing with slow interconnects - https://arxiv.org/abs/2512.10693 - arXiv:2512.10693v1 Announce Type: new -Abstract: The main bottleneck for distributed quantum computing is the rate at which entanglement is produced between quantum processing units (QPUs). In this work, we prove that multiple QPUs connected through slow interconnects can outperform a monolithic architecture made with a single QPU. We consider a distributed quantum computing model with the following assumptions: (1) each QPU is linked to only two other QPUs, (2) each link produces only one Bell pair at a time, (3) the time to generate a Bell pair is $\tau_e$ times longer than the gate time. We propose a distributed version of the CliNR partial error correction scheme respecting these constraints and we show through circuit level simulations that, even if the entanglement generation time $\tau_e$ is up to five times longer than the gate time, distributed CliNR can achieve simultaneously a lower logical error rate and a shorter depth than both the direct implementation and the monolithic CliNR implementation of random Clifford circuits. In the asymptotic regime, we relax assumption (2) and we prove that links producing $O(t/\ln t)$ Bell pairs in parallel, where $t$ is the number of QPUs, is sufficient to avoid stalling distributed CliNR, independently of the number of qubits per QPU. This demonstrates the potential of distributed CliNR for near-term multi-QPU devices. Moreover, we envision a distributed quantum superiority experiment based on the conjugated Clifford circuits of Bouland, Fitzsimons and Koh implemented with distributed CliNR. - oai:arXiv.org:2512.10693v1 + Symbolic Pauli Propagation for Gradient-Enabled Pre-Training of Quantum Circuits + https://arxiv.org/abs/2512.16674 + arXiv:2512.16674v1 Announce Type: new +Abstract: Quantum Machine Learning models typically require expensive on-chip training procedures and often lack efficient gradient estimation methods. By employing Pauli propagation, it is possible to derive a symbolic representation of observables as analytic functions of a circuit's parameters. Although the number of terms in such functional representations grows rapidly with circuit depth, suitable choices of ansatz and controlled truncations on Pauli weights and frequency components yield accurate yet tractable estimators of the target observables. With the right ansatz design, this approach can be extended to system sizes beyond the reach of classical simulation, enabling scalable training for larger quantum systems. This also enables a form of classical pre-training through gradient-based optimization prior to deployment on quantum hardware. The proposed approach is demonstrated on the Variational Quantum Eigensolver for obtaining the ground state of a spin model, showing that accurate results can be achieved with a scalable and computationally efficient procedure. + oai:arXiv.org:2512.16674v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Evan E Dobbs, Nicolas Delfosse, Aharon Brodutch + http://creativecommons.org/licenses/by/4.0/ + Saverio Monaco, Jamal Slim, Florian Rehm, Dirk Kr\"ucker, Kerstin Borras - Sub-Bath Cooling in Bosonic Systems: Gaussian Constraints and Non-Gaussian Enhancements - https://arxiv.org/abs/2512.10703 - arXiv:2512.10703v1 Announce Type: new -Abstract: Cooling quantum systems with finite resources is a central task in quantum technologies and has been extensively explored in discrete-variable settings. As continuous-variable (CV) platforms play an increasingly important role in quantum information processing, it becomes crucial to understand the fundamental limitations of cooling bosonic systems. In this work, we develop a general framework for cooling CV systems, identifying both the constraints imposed by Gaussianity and the advantages enabled by non-Gaussian interactions. We derive a reachable bound on the cooling performance of Gaussian operations that applies to arbitrary cooling architectures. By optimizing over all protocols saturating this bound, we further identify the most efficient scheme, which minimizes dissipated energy for a given number of ancilla modes. Beyond Gaussian operations, we show that $p$-excitation exchange exploits non-Gaussian resources to achieve a $p$-fold enhancement of the cooling limit. Our results establish the fundamental limits of CV heat-bath algorithmic cooling and reveal the crucial role of non-Gaussianity in surpassing Gaussian cooling barriers. - oai:arXiv.org:2512.10703v1 + On the Dynamics of Local Hidden-Variable Models + https://arxiv.org/abs/2512.16682 + arXiv:2512.16682v1 Announce Type: new +Abstract: Bell nonlocality is an intriguing property of quantum mechanics with far reaching consequences for information processing, philosophy and our fundamental understanding of nature. However, nonlocality is a statement about static correlations only. It does not take into account dynamics, i.e. time evolution of those correlations. Consider a dynamic situation where the correlations remain local for all times. Then at each moment in time there exists a local hidden-variable (LHV) model reproducing the momentary correlations. Can the time evolution of the correlations then be captured by evolving the hidden variables? In this light, we define dynamical LHV models and motivate and discuss potential additional physical and mathematical assumptions. Based on a simple counter example we conjecture that such LHV dynamics does not always exist. This is further substantiated by a rigorous no-go theorem. Our results suggest a new type of nonlocality that can be deduced from the observed time evolution of measurement statistics and which generically occurs in interacting quantum systems. + oai:arXiv.org:2512.16682v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Wen-Han Png, Xueyuan Hu, Valerio Scarani + Nick von Selzam, Florian Marquardt - Scalable Optical Links for Controlling Bosonic Quantum Processors - https://arxiv.org/abs/2512.10706 - arXiv:2512.10706v1 Announce Type: new -Abstract: Superconducting quantum computing has the potential to revolutionize computational capabilities. However, scaling up large quantum processors is limited by the cumbersome and heat-conductive electronic cables that connect room-temperature control electronics to quantum processors, leading to significant signal attenuation. Optical fibers provide a promising solution, but their use has been restricted to controlling simple two-level quantum systems over short distances. Here, we demonstrate optical control of a bosonic quantum processor, achieving universal operations on the joint Hilbert space of a transmon qubit and a storage cavity. Using an array of cryogenic fiber-integrated uni-traveling-carrier photodiodes, we prepare Fock states containing up to ten photons. Additionally, remote control of bosonic modes over a transmission distance of 15 km has been achieved, with fidelities exceeding 95%. The combination of high-dimensional quantum control, multi-channel operation, and long-distance transmission addresses the key requirements for scaling superconducting quantum computers and enables architectures for distributed quantum data centers. - oai:arXiv.org:2512.10706v1 + Propagators of singular anharmonic oscillators with quasi-equidistant spectra + https://arxiv.org/abs/2512.16695 + arXiv:2512.16695v1 Announce Type: new +Abstract: Darboux transformations of the singular harmonic oscillator are considered. Analytical expressions for the propagators are obtained, using the image method applied to formal singular propagators. Two-well and three-well families of potentials and the corresponding propagators are presented. Axially symmetric magnetic field configurations corresponding to these potentials have been identified. + oai:arXiv.org:2512.16695v1 quant-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + math-ph + math.MP + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Chuanlong Ma, Jia-Qi Wang, Linze Li, Jiajun Chen, Xiaoxuan Pan, Zheng-Hui Tian, Zheng-Xu Zhu, Jia-Hua Zou, Dingran Gu, Luyu Wang, Qiushi Chen, Weiting Wang, Xin-Biao Xu, Chang-Ling Zou, Baile Chen, Luyan Sun + Andrey M. Pupasov-Maksimov, Marcelo Silva Oliveira - Further Statistical Study of NISQ Experiments - https://arxiv.org/abs/2512.10722 - arXiv:2512.10722v1 Announce Type: new -Abstract: We revisit and extend some topics that we studied in our previous works (Rinott, Kalai and Shoham 2022; Kalai, Rinott and Shoham, 2023,2024) regarding the Google 2019 "quantum supremacy" experiment. We extend our analysis of the prediction based on Google's digital error model (Formula (77)), based on more detailed data provided by Google. We also provide some preliminary analysis for a few other NISQ experiments. - oai:arXiv.org:2512.10722v1 + QuantumSavory: Write Symbolically, Run on Any Backend -- A Unified Simulation Toolkit for Quantum Computing and Networking + https://arxiv.org/abs/2512.16752 + arXiv:2512.16752v1 Announce Type: new +Abstract: Progress in quantum computing and networking depends on codesign across abstraction layers: device-level noise and heterogeneous hardware, algorithmic structure, and distributed classical control. We present QuantumSavory, an open-source toolkit built to make such end-to-end studies practical by cleanly separating a symbolic computer-algebra frontend from interchangeable numerical simulation backends. States, operations, measurements, and protocol logic are expressed in a backend-agnostic symbolic language; the same model can be executed across multiple backends (e.g., stabilizer, wavefunction, phase-space), enabling rapid exploration of accuracy-performance tradeoffs without rewriting the model. Furthermore, new custom backends can be added via a small, well-defined interface that immediately reuses existing models and protocols. + QuantumSavory also addresses the classical-quantum interaction inherent to LOCC protocols via discrete-event execution and a tag/query system for coordination. Tags attach structured classical metadata to quantum registers and message buffers, and queries retrieve, filter, or wait on matching metadata by wildcards or arbitrary predicates. This yields a data-driven control plane where protocol components coordinate by publishing and consuming semantic facts (e.g., resource availability, pairing relationships, protocol outcomes) rather than by maintaining rigid object graphs or bespoke message plumbing, improving composability and reuse as models grow. Our toolkit is also not limited to qubits and Bell pairs; rather, any networking dynamics of any quantum system under any type of multipartite entanglement can be tackled. Lastly, QuantumSavory ships reusable libraries of standard states, circuits, and protocol building blocks with consistent interfaces, enabling full-stack examples to be assembled, modified, and compared with minimal glue code. + oai:arXiv.org:2512.16752v1 quant-ph - cs.CC - stat.AP - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Gil Kalai, Tomer Shoham, Carsten Voelkmann + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Hana KimLee, Leonardo Bacciottini, Abhishek Bhatt, Andrew Kille, Stefan Krastanov - Understanding Surface-Induced Decoherence of NV Centers in Diamond - https://arxiv.org/abs/2512.10726 - arXiv:2512.10726v1 Announce Type: new -Abstract: Nitrogen vacancy centers (NV) in proximity to diamond surfaces are promising nanoscale quantum sensors. However, their coherence properties are negatively affected by magnetic and electric surface noise, whose origin and detailed impact have remained elusive. Using atomistic models of diamond surfaces derived with density functional theory, together with decoherence time calculations with cluster correlation expansion methods, we quantify the effects of surface crystallographic orientation and functionalization, and of the density of unpaired electrons on the NV Hahn-echo time $T_2$. We determine a crossover depth at which $T_2$ ceases to be limited by surface nuclear spins and recovers the bulk-limited value. We find that for static surface-electron baths, the ratio between the NV depth and the separation between surface electron spins determines a transition from fast-fluctuating to quasi-static noise, leading to a dependence of $T_2$ on orientation for specific surfaces. We also find that the modulation of $T_2$ by spin-phonon relaxations leads to motional-narrowing at sub-microsecond relaxation times. Importantly, our calculations show that it is only when accounting for surface-spin in-sequence hopping that measured $T_2$ values as a function of depth can be reproduced, thus highlighting the importance of hopping-mediated models to describe the surface spin noise affecting NV sensors. Overall, our work provides clear guidelines for engineering diamond surfaces to achieve enhanced NV coherence for quantum sensing and information processing applications. - oai:arXiv.org:2512.10726v1 + Reconstruction of Quantum Fields + https://arxiv.org/abs/2512.16775 + arXiv:2512.16775v1 Announce Type: new +Abstract: One of the traditional ways of introducing bosons and fermions is through creation and annihilation algebras. Historically, these have been associated with emission and absorption processes at the quantum level and are characteristic of the language of second quantization. In this work, we formulate the transition from first to second quantization by taking quotients of the state spaces of distinguishable particles, so that the resulting equivalence classes identify states that contain no information capable of distinguishing between particles, thereby generalising the usual symmetrisation procedure. Assuming that the resulting indistinguishable-particle space (i) admits an ordered basis compatible with how an observer may label the accessible modes, (ii) is invariant under unitary transformations of those modes, and (iii) supports particle counting as a mode-wise local operation, we derive a new class of creation-annihilation algebras. These algebras reproduce the partition functions of transtatistics-maximal generalisations of bosons and fermions consistent with these operational principles. + oai:arXiv.org:2512.16775v1 quant-ph - cond-mat.mes-hall - cond-mat.mtrl-sci - Fri, 12 Dec 2025 00:00:00 -0500 + math-ph + math.MP + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Jonah Nagura, Mykyta Onizhuk, Giulia Galli + Nicol\'as Medina S\'anchez, Borivoje Daki\'c - Complexity and multi-functional variants of the Quantum-to-Quantum Bernoulli Factories - https://arxiv.org/abs/2512.10810 - arXiv:2512.10810v1 Announce Type: new -Abstract: A Bernoulli factory is a model for randomness manipulation that transforms an initial Bernoulli random variable into another Bernoulli variable by applying a predetermined function relating the output bias to the input one. In literature, quantum-to-quantum Bernoulli factory schemes have been proposed, which encode both the input and output variables using qubit amplitudes. This fundamental concept can serve as a subroutine for quantum algorithms that involve Bayesian inference and Monte Carlo methods, or that require data encryption, like in blind quantum computation. In this work, we present a characterisation of the complexity of the quantum-to-quantum Bernoulli factory by providing a lower bound on the required number of qubits needed to implement the protocol, an upper bound on the success probability and the quantum circuit that saturates the bounds. We also formalise and analyse two different variants of the original problem that address the possibility of increasing the number of input biases or the number of functions implemented by the quantum-to-quantum Bernoulli factory. The obtained results can be used as a framework for randomness manipulation via such an approach. - oai:arXiv.org:2512.10810v1 + A magic criterion (almost) as nice as PPT, with applications in distillation and detection + https://arxiv.org/abs/2512.16777 + arXiv:2512.16777v1 Announce Type: new +Abstract: We introduce a mixed-state magic criterion, the Triangle Criterion, which plays a role for magic analogous to the Positive Partial Transposition (PPT) criterion for entanglement: it combines strong detection capability, a clear geometric interpretation, and an operational link to magic distillation. Using this criterion, we uncover several new features of multi-qubit magic distillation and detection. We prove that genuinely multi-qubit magic distillation protocols are strictly more powerful than all single-qubit schemes by showing that the Triangle Criterion is not stable under tensor products, in sharp contrast to the PPT criterion. Moreover, we show that, with overwhelming probability, multi-qubit magic states with relatively low rank cannot be distilled by any single-qubit distillation protocol. We derive an upper bound on the minimal purity of magic states, which is conjectured to be tight with both numerical and constructive evidences. Using this minimal-purity result, we predict the existence of unfaithful magic states, namely states that cannot be detected by any fidelity-based magic witness, and reveal fundamental limitations of mixed-state magic detection in any single-copy scheme. + oai:arXiv.org:2512.16777v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Francesco Hoch, Taira Giordani, Gonzalo Carvacho, Nicol\`o Spagnolo, Fabio Sciarrino + Zhenhuan Liu, Tobias Haug, Qi Ye, Zi-Wen Liu, Ingo Roth - Quantum Approaches to Urban Logistics: From Core QAOA to Clustered Scalability - https://arxiv.org/abs/2512.10813 - arXiv:2512.10813v1 Announce Type: new -Abstract: The Traveling Salesman Problem (TSP) is a fundamental challenge in combinatorial optimization, widely applied in logistics and transportation. As the size of TSP instances grows, traditional algorithms often struggle to produce high-quality solutions within reasonable timeframes. This study investigates the potential of the Quantum Approximate Optimization Algorithm (QAOA), a hybrid quantum-classical method, to solve TSP under realistic constraints. We adopt a QUBO-based formulation of TSP that integrates real-world logistical constraints reflecting operational conditions, such as vehicle capacity, road accessibility, and time windows, while ensuring compatibility with the limitations of current quantum hardware. Our experiments are conducted in a simulated environment using high-performance computing (HPC) resources to assess QAOA's performance across different problem sizes and quantum circuit depths. In order to improve scalability, we propose clustering QAOA (Cl-QAOA), a hybrid approach combining classical machine learning with QAOA. This method decomposes large TSP instances into smaller sub-problems, making quantum optimization feasible even on devices with a limited number of qubits. The results offer a comprehensive evaluation of QAOA's strengths and limitations in solving constrained TSP scenarios. This study advances quantum optimization and lays groundwork for future large-scale applications. - oai:arXiv.org:2512.10813v1 + Non-Linear Strong Data-Processing for Quantum Hockey-Stick Divergences + https://arxiv.org/abs/2512.16778 + arXiv:2512.16778v1 Announce Type: new +Abstract: Data-processing is a desired property of classical and quantum divergences and information measures. In information theory, the contraction coefficient measures how much the distinguishability of quantum states decreases when they are transmitted through a quantum channel, establishing linear strong data-processing inequalities (SDPI). However, these linear SDPI are not always tight and can be improved in most of the cases. In this work, we establish non-linear SDPI for quantum hockey-stick divergence for noisy channels that satisfy a certain noise criterion. We also note that our results improve upon existing linear SDPI for quantum hockey-stick divergences and also non-linear SDPI for classical hockey-stick divergence. We define $F_\gamma$ curves generalizing Dobrushin curves for the quantum setting while characterizing SDPI for the sequential composition of heterogeneous channels. In addition, we derive reverse-Pinsker type inequalities for $f$-divergences with additional constraints on hockey-stick divergences. We show that these non-linear SDPI can establish tighter finite mixing times that cannot be achieved through linear SDPI. Furthermore, we find applications of these in establishing stronger privacy guarantees for the composition of sequential private quantum channels when privacy is quantified by quantum local differential privacy. + oai:arXiv.org:2512.16778v1 quant-ph + cs.CR + cs.IT cs.LG - Fri, 12 Dec 2025 00:00:00 -0500 + math.IT + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - F. Picariello, G. Turati, R. Antonelli, I. Bailo, S. Bonura, G. Ciarfaglia, S. Cipolla, P. Cremonesi, M. Ferrari Dacrema, M. Gabusi, I. Gentile, V. Morreale, A. Noto + Theshani Nuradha, Ian George, Christoph Hirche - Estimating Detector Error Models on Google's Willow - https://arxiv.org/abs/2512.10814 - arXiv:2512.10814v1 Announce Type: new -Abstract: We consolidate recent theoretical advances in Detector Error Model (DEM) estimation and formalize several algorithms to learn DEM parameters and structure from syndromes without using a decoder, demonstrating recovery of known DEMs from simulated syndromes with precision limited only by finite-sample effects. We then apply these algorithms to estimate DEMs from Google's 72- and 105-qubit chips. Using a likelihood function that is tractable for small DEMs, we show that DEMs estimated directly from syndromes agree more closely with unseen syndromes than DEMs trained to optimize logical performance, whereas the latter outperform the former as priors for decoders in logical memory experiments. We used a time-series of estimated DEMs to track both global error and specific local errors over the course of a QEC experiment, suggesting applications in online characterization. We employ a sequence of DEM estimation techniques to discover and quantify long-range detector correlations spanning the width of the 105-qubit chip, for which DEM analysis suggests correlated measurement errors rather than high-weight Pauli errors as the most likely explanation. Finally, we present two artifacts in repetition code syndromes that are \emph{not} well-modeled by a DEM: correlated flipping of pairs of adjacent detectors in many consecutive rounds of QEC, and signatures consistent with radiation events occurring more frequently than previously reported. - oai:arXiv.org:2512.10814v1 + Numerically exact open quantum system work statistics with process tensors + https://arxiv.org/abs/2512.16823 + arXiv:2512.16823v1 Announce Type: new +Abstract: Accurately quantifying the thermodynamic work costs of quantum operations is essential for the continued development and optimisation of emerging quantum technologies. This present a significant challenge in regimes of rapid control within complex, non-equilibrium environments - conditions under which many contemporary quantum devices operate and conventional approximations break down. Here, we introduce a process tensor framework that enables the computation of the full numerically exact quantum work statistics of driven open quantum systems. We demonstrate the utility of our approach by applying it to a Landauer erasure protocol operating beyond the weak-coupling, Markovian, and slow-driving limits. The resulting work probability distributions reveal distinct quantum signatures that are missed by low-order moments yet significantly impact the erasure fidelity of the protocol. Our framework delivers non-perturbative accuracy and detail in characterising energy-exchange fluctuations in driven open quantum systems, establishing a powerful and versatile tool for exploring thermodynamics and control in the operating regimes of both near-term and future quantum devices. + oai:arXiv.org:2512.16823v1 quant-ph - physics.data-an - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.mes-hall + cond-mat.stat-mech + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Kregg Elliot Arms, Martin James McHugh, Joseph Edward Nyhan, William Frederick Reus, James Loudon Ulrich + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Mike Shubrook, Moritz Cygorek, Erik Gauger, Jake Iles-Smith, Ahsan Nazir - Optimized Measurement Schedules for the Surface Code with Dropout - https://arxiv.org/abs/2512.10871 - arXiv:2512.10871v1 Announce Type: new -Abstract: Recent work has shown that fabrication defects can be well-handled using a strategy relying on the mid-error-correction-cycle state. In this work we present two improvements to the original prescription. First, we quantify the impact of the choice of a more complete set of gauge operators originally proposed for the hex-grid surface code on the standard square-grid surface code, as well as a new method for excising effectively unused qubits. Second, we leverage the expressivity of the LUCI framework as an intermediate representation, using integer linear programming to find performant physical circuits from the large space of valid LUCI circuits. We show that on the $d = 11$ surface code at $1\%(3\%)$ dropout rate for qubits and couplers, these optimizations allow for a total improvement of $14.5\%(23.6\%)$ over $4d$ round of syndrome extraction using the SI1000 noise model at $0.1\%$ noise. - oai:arXiv.org:2512.10871v1 + Nonstabilizerness in Stark many-body localization + https://arxiv.org/abs/2512.16859 + arXiv:2512.16859v1 Announce Type: new +Abstract: Quantum many-body disorder-free localization can suppress transport while still allowing the buildup of computationally costly non-Clifford resources. In a transverse-field Ising chain realizing disorder-free Stark many-body localization, we show that the stabilizer R\'enyi entropy remains nonzero and grows slowly to a finite plateau deep in the strong Stark-field regime, with strong initial-state selectivity. As the Stark field strength increases, long-time magic and entanglement consistently signal a crossover from ergodic to constrained localized dynamics. These results establish nonstabilizerness (``magic'') as a practical complexity probe for disorder-free ergodicity breaking and constrained localization, with direct relevance to benchmarking and designing near-term quantum simulators, and fill a gap in the understanding of nonstabilizerness in disorder-free many-body localization. + oai:arXiv.org:2512.16859v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Benjamin Anker, Dripto M. Debroy + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Han-Ze Li, Yi-Rui Zhang, Yu-Jun Zhao, Xuyang Huang, Jian-Xin Zhong - Multiple-time Quantum Imaginary Time Evolution - https://arxiv.org/abs/2512.10875 - arXiv:2512.10875v1 Announce Type: new -Abstract: Quantum Imaginary-Time Evolution (QITE) is a powerful method for preparing ground states on quantum hardware. However, executing QITE has costly measurement budgets for general Hamiltonians. Both fidelity and computational cost are strongly dependent on the definition of suitable local domains and Hamiltonian partitions. In this work, we introduce the Multiple-Time QITE algorithm (MT-QITE). We show how using more than one imaginary time substantially improves the fidelity of the resulting ground state as well as the measurement overhead with respect to the previously published QITE algorithm, while preserving its deterministic character and its independence from ad hoc ansatze. Moreover, unlike QITE and other QITE-based algorithms, MT-QITE is parallelizable, and we show that even in Hamiltonians with non-local interactions, partitioning may entail a computational advantage. - oai:arXiv.org:2512.10875v1 + Random purification channel for passive Gaussian bosons + https://arxiv.org/abs/2512.16878 + arXiv:2512.16878v1 Announce Type: new +Abstract: The random purification channel, which, given $n$ copies of an unknown mixed state $\rho$, prepares $n$ copies of an associated random purification, has proved to be an extremely valuable tool in quantum information theory. In this work, we construct a Gaussian version of this channel that, given $n$ copies of a bosonic passive Gaussian state, prepares $n$ copies of one of its randomly chosen Gaussian purifications. The construction has the additional advantage that each purification has a mean photon number which is exactly twice that of the initial state. Our construction relies on the characterisation of the commutant of passive Gaussian unitaries via the representation theory of dual reductive pairs of unitary groups. + oai:arXiv.org:2512.16878v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.other + math-ph + math.MP + Fri, 19 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Julio Del Castillo, Mats Granath, Evert van Nieuwenburg + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Francesco Anna Mele, Filippo Girardi, Senrui Chen, Marco Fanizza, Ludovico Lami - ENTCALC: Toolkit for calculating geometric entanglement in multipartite quantum systems - https://arxiv.org/abs/2512.10884 - arXiv:2512.10884v1 Announce Type: new -Abstract: We present entcalc, a Python and MATLAB package for estimating the geometric entanglement of multipartite quantum states. The package operates as follows: given a multipartite quantum state as input, it outputs an estimate of its geometric entanglement. For pure states, it computes the geometric entanglement together with an estimation error. For mixed states, it provides both lower and upper bounds on the geometric entanglement, thereby identifying an interval in which the true value lies. We provide several methods to compute the lower bound, enabling users to balance accuracy against computational cost. We apply entcalc to several representative examples, including for $3\otimes3$ PPT entangled states, mixtures of GHZ and W states, thermal states of selected three-qubit spin chains, and noisy GHZ and W states. We observe signatures of quantum phase transitions by quantifying entanglement in spin chains. We also demonstrate that entanglement between non-neighbouring sites can be activated by tuning the external magnetic field. In all tested cases, the gap between the lower and upper bounds is found to be very small, indicating that entcalc provides highly accurate estimates of the geometric entanglement for these states. - oai:arXiv.org:2512.10884v1 + Advantage of Warm Starts for Electron-Phonon Systems on Quantum Computers + https://arxiv.org/abs/2512.16879 + arXiv:2512.16879v1 Announce Type: new +Abstract: Simulating electron-phonon interactions on quantum computers remains challenging, with most algorithmic effort focused on Hamiltonian simulation and circuit optimization. In this work, we study the single-electron Holstein model and propose an initial-state ansatz that substantially enhances ground state overlap in the strong coupling regime, thereby reducing the number of iterations required in standard quantum phase estimation. We further show that this ansatz can be implemented efficiently and yields an exponential reduction in overall circuit costs relative to conventional initial guesses. Our results highlight the practical value of incorporating physical intuition into initial state preparation for electron-phonon coupled systems. + oai:arXiv.org:2512.16879v1 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Piotr Masajada, Aby Philip, Alexander Streltsov + Arnab Adhikary, S. E. Skelton, Alberto Nocera, Mona Berciu - Quantifying classical and quantum bounds for resolving closely spaced, non-interacting, simultaneously emitting dipole sources in optical microscopy - https://arxiv.org/abs/2512.10889 - arXiv:2512.10889v1 Announce Type: new -Abstract: Recent theoretical and experimental work has shown that the quantum Fisher information associated with estimating the separation between two optical point sources remains finite at small separations, effectively opening new routes to super-resolution imaging of simultaneously emitting sources. Most studies to date, however, implicitly invoke the scalar approximation, which is not appropriate in the context of high-numerical-aperture microscopy. Utilizing parameter estimation theory, here we consider the estimation of separation between two closely spaced dipole emitters, a commonly employed model for single-molecule optical beacons. We consider two limiting cases: one in which the orientations of the emitters are fixed and equal, and another in which both dipoles freely sample all of orientation space over the course of the measurement. We quantify precision limits using quantum and classical variants of the Fisher information and Cram\'{e}r-Rao bound. In all cases, the vectorial nature of the emission complicates the analyses, but with appropriate filtering of the collected light in the azimuthal-radial polarization basis, a previously proposed scheme to saturate the quantum Fisher information via image inversion interferometry can be salvaged. - oai:arXiv.org:2512.10889v1 + Many-body contextuality and self-testing quantum matter via nonlocal games + https://arxiv.org/abs/2512.16886 + arXiv:2512.16886v1 Announce Type: new +Abstract: Contextuality is arguably the fundamental property that makes quantum mechanics different from classical physics. It is responsible for quantum computational speedups in both magic-state-injection-based and measurement-based models of computation, and can be directly probed in a many-body setting by multiplayer nonlocal quantum games. Here, we discuss a family of games that can be won with certainty when performing single-site Pauli measurements on a state that is a codeword of a Calderbank-Shor-Steane (CSS) error-correcting quantum code. We show that these games require deterministic computation of a code-dependent Boolean function, and that the classical probability of success is upper bounded by a generalized notion of nonlinearity/nonquadraticity. This success probability quantifies the state's contextuality, and is computed via the function's (generalized) Walsh-Hadamard spectrum. To calculate this, we introduce an efficient, many-body-physics-inspired method that involves identifying the symmetries of an auxiliary hypergraph state. We compute the classical probability of success for several paradigmatic CSS codes and relate it to both classical statistical mechanics models and to strange correlators of symmetry-protected topological states. We also consider CSS submeasurement games, which can only be won with certainty by sharing the appropriate codeword up to local isometries. These games therefore enable self-testing, which we illustrate explicitly for the 2D toric code. We also discuss how submeasurement games enable an extensive notion of contextuality in many-body states. + oai:arXiv.org:2512.16886v1 quant-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + cond-mat.str-el + Fri, 19 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Armine I. Dingilian, Aarnah Kurella, Cheyenne S. Mitchell, Dhananjay Dhruva, David J. Durden, Mikael P. Backlund + Oliver Hart, David T. Stephen, Evan Wickenden, Rahul Nandkishore - Partitioned Expansions for Approximate Tensor Network Contractions - https://arxiv.org/abs/2512.10910 - arXiv:2512.10910v1 Announce Type: new -Abstract: We propose a method for approximating the contraction of a tensor network by partitioning the network into a sum of computationally cheaper networks. This method, which we call a partitioned network expansion (PNE), builds upon recent work that systematically improves belief propagation (BP) approximations using loop corrections. However, in contrast to previous approaches, our expansion does not require a known BP fixed point to be implemented and can still yield accurate results even in cases where BP fails entirely. The flexibility of our approach is demonstrated through applications to a variety of example networks, including finite 2D and 3D networks, infinite networks, networks with open indices, and networks with degenerate BP fixed points. Benchmark numerical results for networks composed of Ising, AKLT, and random tensors typically show an improvement in accuracy over BP by several orders of magnitude (when BP solutions are obtainable) and also demonstrate improved performance over traditional network approximations based on singular value decomposition (SVD) for certain tasks. - oai:arXiv.org:2512.10910v1 + Anubuddhi: A Multi-Agent AI System for Designing and Simulating Quantum Optics Experiments + https://arxiv.org/abs/2512.15736 + arXiv:2512.15736v1 Announce Type: cross +Abstract: We present Anubuddhi, a multi-agent AI system that designs and simulates quantum optics experiments from natural language prompts without requiring specialized programming knowledge. The system composes optical layouts by arranging components from a three-tier toolbox via semantic retrieval, then validates designs through physics simulation with convergent refinement. The architecture combines intent routing, knowledge-augmented generation, and dual-mode validation (QuTiP and FreeSim). We evaluated 13 experiments spanning fundamental optics (Hong-Ou-Mandel interference, Michelson/Mach-Zehnder interferometry, Bell states, delayed-choice quantum eraser), quantum information protocols (BB84 QKD, Franson interferometry, GHZ states, quantum teleportation, hyperentanglement), and advanced technologies (boson sampling, electromagnetically induced transparency, frequency conversion). The system achieves design-simulation alignment scores of 8--9/10, with simulations faithfully modeling intended physics. A critical finding distinguishes structural correctness from quantitative accuracy: high alignment confirms correct physics architecture, while numerical predictions require expert review. Free-form simulation outperformed constrained frameworks for 11/13 experiments, revealing that quantum optics diversity demands flexible mathematical representations. The system democratizes computational experiment design for research and pedagogy, producing strong initial designs users can iteratively refine through conversation. + oai:arXiv.org:2512.15736v1 + cs.AI + cs.LG quant-ph - cond-mat.str-el - Fri, 12 Dec 2025 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Glen Evenbly, Johnnie Gray, Garnet Kin-Lic Chan + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-sa/4.0/ + S. K. Rithvik - Qubit decoherence in dissipative two-photon resonator: real-time instantons and Wigner function - https://arxiv.org/abs/2512.10921 - arXiv:2512.10921v1 Announce Type: new -Abstract: We study the quantum dynamics of a single bosonic cavity subject to two-photon driving and two-photon dissipation in the presence of finite detuning. Exploiting a hidden time-reversal symmetry, the Wigner representation and the WKB method, we introduce an effective phase-space potential for description of the steady state. It reveals two attracting points, which are metastable due to quantum fluctuations. By employing the Keldysh real-time path integral formalism, we compute the instanton trajectory governing the quantum activation process between these attractors and establish a fundamental connection with the Wigner representation. This relation unifies the steady-state phase-space description with dynamical quantum activation processes. We also derive an analytical expression for the decoherence rate of the system. Our work provides a coherent theoretical framework for analyzing quantum bistability, metastability, and decoherence in driven-dissipative nonlinear resonators, with direct implications for the design of bosonic qubits and quantum information processing. - oai:arXiv.org:2512.10921v1 + Localization from Infinitesimal Kinetic Grading: Critical Scaling and Kibble-Zurek Universality + https://arxiv.org/abs/2512.15795 + arXiv:2512.15795v1 Announce Type: cross +Abstract: We study a one-dimensional lattice model with site-dependent nearest-neighbor hopping amplitudes that follow a power-law profile. The hopping variation is controlled by a grading exponent, $\alpha$, which serves as the tuning parameter of the system. In the thermodynamic limit, the ground state becomes localized as $|\alpha| \to 0$, signaling the presence of a critical point characterized by a diverging localization length. Using exact diagonalization, we perform finite-size scaling analysis and extract the associated critical exponent governing this divergence, revealing a universality class distinct from well-known Anderson, Aubry-Andre, and Stark localization. To further characterize the critical behavior, we analyze the inverse participation ratio, the energy gap between the ground and first excited states, and the fidelity susceptibility. We also investigate nonequilibrium dynamics by linearly ramping the hopping profile at various rates and tracking the evolution of the localization length and the inverse participation ratio. The Kibble-Zurek mechanism successfully captures the resulting dynamics using the critical exponents obtained from the static scaling analysis. Our results demonstrate a clean, disorder-free route to localization and provide a tunable platform relevant to photonic lattices and ultracold atom arrays with engineered hopping profiles. + oai:arXiv.org:2512.15795v1 + cond-mat.quant-gas quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 - new - http://creativecommons.org/licenses/by/4.0/ - V. Yu. Mylnikov, S. O. Potashin, Alex Kamenev + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Argha Debnath, Ayan Sahoo, Debraj Rakshit - Noisy Quantum Learning Theory - https://arxiv.org/abs/2512.10929 - arXiv:2512.10929v1 Announce Type: new -Abstract: We develop a framework for learning from noisy quantum experiments, focusing on fault-tolerant devices accessing uncharacterized systems through noisy couplings. Our starting point is the complexity class $\textsf{NBQP}$ ("noisy BQP"), modeling noisy fault-tolerant quantum computers that cannot, in general, error-correct the oracle systems they query. Using this class, we show that for natural oracle problems, noise can eliminate exponential quantum learning advantages of ideal noiseless learners while preserving a superpolynomial gap between NISQ and fault-tolerant devices. Beyond oracle separations, we study concrete noisy learning tasks. For purity testing, the exponential two-copy advantage collapses under a single application of local depolarizing noise. Nevertheless, we identify a setting motivated by AdS/CFT in which noise-resilient structure restores a quantum learning advantage in a noisy regime. We then analyze noisy Pauli shadow tomography, deriving lower bounds that characterize how instance size, quantum memory, and noise control sample complexity, and design algorithms with parametrically similar scalings. Together, our results show that the Bell-basis and SWAP-test primitives underlying most exponential quantum learning advantages are fundamentally fragile to noise unless the experimental system has latent noise-robust structure. Thus, realizing meaningful quantum advantages in future experiments will require understanding how noise-robust physical properties interface with available algorithmic techniques. - oai:arXiv.org:2512.10929v1 + Lanczos Meets Orthogonal Polynomials + https://arxiv.org/abs/2512.15857 + arXiv:2512.15857v1 Announce Type: cross +Abstract: We establish a direct correspondence between the Lanczos approach and the orthogonal polynomials approach in random matrix theory. In the large-$N$ and continuum limits, the average Lanczos coefficients and the recursion coefficients become equivalent, with the precise mapping $\sqrt{R(x)} = b(1-x)$ and $S(x) = a(1-x)$. As a result, the two formalisms yield identical expressions for the leading density of states. We further analyze the Krylov dynamics associated with the recursion coefficients and show that the orthogonal polynomials admit a natural interpretation as Krylov polynomials. This picture is realized explicitly in the Gaussian Unitary Ensemble, where all quantities can be computed analytically. + oai:arXiv.org:2512.15857v1 + hep-th quant-ph - cs.CC - cs.IT - cs.LG - math.IT - Fri, 12 Dec 2025 00:00:00 -0500 - new + Fri, 19 Dec 2025 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jordan Cotler, Weiyuan Gong, Ishaan Kannan + Le-Chen Qu - QSTAformer: A Quantum-Enhanced Transformer for Robust Short-Term Voltage Stability Assessment against Adversarial Attacks - https://arxiv.org/abs/2512.09936 - arXiv:2512.09936v1 Announce Type: cross -Abstract: Short-term voltage stability assessment (STVSA) is critical for secure power system operation. While classical machine learning-based methods have demonstrated strong performance, they still face challenges in robustness under adversarial conditions. This paper proposes QSTAformer-a tailored quantum-enhanced Transformer architecture that embeds parameterized quantum circuits (PQCs) into attention mechanisms-for robust and efficient STVSA. A dedicated adversarial training strategy is developed to defend against both white-box and gray-box attacks. Furthermore, diverse PQC architectures are benchmarked to explore trade-offs between expressiveness, convergence, and efficiency. To the best of our knowledge, this is the first work to systematically investigate the adversarial vulnerability of quantum machine learning-based STVSA. Case studies on the IEEE 39-bus system demonstrate that QSTAformer achieves competitive accuracy, reduced complexity, and stronger robustness, underscoring its potential for secure and scalable STVSA under adversarial conditions. - oai:arXiv.org:2512.09936v1 - eess.SY - cs.LG - cs.SY + Classifying one-dimensional Floquet phases through two-dimensional topological order + https://arxiv.org/abs/2512.15868 + arXiv:2512.15868v1 Announce Type: cross +Abstract: Floquet systems display rich phenomena, such as time crystals, with many-body localisation (MBL) protecting the phases from heating. While several types of Floquet phases have been classified, a unified picture of Floquet MBL is still emerging. Static phases have been fruitfully studied via "symmetry topological field theory" (SymTFT), wherein the universal features of $G$-symmetric systems are elucidated by placing them on the boundary of a topological order of one dimension higher. In this work, we provide a SymTFT approach to classifying $G$-symmetric Floquet MBL phases in 1D, for $G$ a finite Abelian group with on-site unitary action. In the SymTFT, these 1D systems correspond to the boundaries of the quantum double associated to $G$, and the classification naturally arises from considering the Lagrangian subgroups and boundary excitations of the quantum double. The classification covers all known Floquet phases while uncovering others previously unexplored, along with bulk features of phases thought to have only boundary signatures. We refer to the latter phases as "dual" time crystals. For static phases, we show how anyons of the quantum double and (string) order parameters provide a natural and simple interpretation of known classification schemes. By extending our framework to the boundaries of twisted quantum doubles, we uncover a new time-crystalline phase with non-onsite symmetry, which cannot be obtained through local, symmetric Hamiltonian drives. We numerically demonstrate evidence for the absolute stability of this phase, and observe that for open boundary conditions it has greater stability to symmetric perturbations. We finally discuss perspectives on using programmable quantum devices to realise and probe the phases we discuss. Our results show that SymTFT provides a powerful approach to unifying phases and features of Floquet systems. + oai:arXiv.org:2512.15868v1 + cond-mat.str-el + hep-th quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yang Li, Chong Ma, Yuanzheng Li, Sen Li, Yanbo Chen, Zhaoyang Dong + Campbell McLauchlan, Vedant Motamarri, Benjamin B\'eri - Quantum Monte Carlo in Classical Phase Space with the Wigner-Kirkwood Commutation Function. Results for the Saturation Liquid Density of $^4$He - https://arxiv.org/abs/2512.09948 - arXiv:2512.09948v1 Announce Type: cross -Abstract: A Metropolis Monte Carlo algorithm is given for the case of a complex phase space weight, which applies generally in quantum statistical mechanics. Computer simulations using Lennard-Jones $^4$He near the $\lambda$-transition, including an expansion to third order of the Wigner-Kirkwood commutation function, give a saturation liquid density in agreement with measured values. - oai:arXiv.org:2512.09948v1 - cond-mat.stat-mech - cond-mat.quant-gas - physics.comp-ph + Tree Tensor Networks Methods for Efficient Calculation of Molecular Vibrational Spectra + https://arxiv.org/abs/2512.15875 + arXiv:2512.15875v1 Announce Type: cross +Abstract: We develop and employ general Tree Tensor Networks (TTNs) to compute the vibrational spectra for two model systems: a set of 64-dimensional coupled oscillators and acetonitrile. We explore various tree architectures, ranging from the simple linear structure of Matrix Product States (MPS), to trees where only the leaf nodes carry a physical leg -- as seen in the underlying ansatz of the Multilayer Multiconfiguration Time-Dependent Hartree (ML-MCTDH) method -- and further to more general trees in which all nodes are allowed to possess a physical leg. In addition, we implement Locally Optimal Block Preconditioned Conjugate Gradient (LOBPCG) methods and Inverse Iteration methods as eigensolvers. By means of comprehensive benchmarking of runtime and accuracy, we demonstrate that sub-wavenumber accuracy in vibrational spectra is achievable with all TTN structures. MPS and three-legged tree tensor network states (T3NS) have similar runtimes, whereas leaf-only trees require significantly more time. All numerical simulations were performed using PyTreeNet, a Python package designed for flexible tensor network computations. + oai:arXiv.org:2512.15875v1 + physics.chem-ph + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-sa/4.0/ + Shuo Sun, Richard M. Milbradt, Stefan Knecht, Chandan Kumar, Christian B. Mendl + + + Entangled two-proton emission from 16Ne and its sensitivity to diproton correlation + https://arxiv.org/abs/2512.15879 + arXiv:2512.15879v1 Announce Type: cross +Abstract: We discuss how the spin correlation, which reflects the quantum entanglement between two fermions, can serve as a probe of diproton correlation in the two-proton ($2p$) emission. We investigated the 16Ne nucleus using the time-dependent three-body (14O + 2p) model, and found that the $2p$-spin correlation exceeded the limit of local-hidden-variable (LHV) theory when the initial state had a spin-singlet diproton configuration. In contrast, for other configurations, it was remarkably reduced. This suggests that a strong initial diproton correlation is essential to generate a spin correlation nearly identical to that of a pure spin-singlet diproton. Such sensitivity indicates that $2p$-spin correlation can serve as a sensitive probe of diproton configurations, which could facilitate future studies on quantum entanglement and spin-dependent phenomena in atomic nuclei as well as in broader multi-fermion systems. + oai:arXiv.org:2512.15879v1 + nucl-th + nucl-ex quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Phil Attard + Tomohiro Oishi, Masaaki Kimura - Measuring the Hall Viscosity of the Laughlin State on Noisy Quantum Computers - https://arxiv.org/abs/2512.09982 - arXiv:2512.09982v1 Announce Type: cross -Abstract: Hall viscosity is a quantized nondissipative stress response of a fractional quantum Hall (FQH) fluid to adiabatic geometric deformations. Despite strong theoretical interest, its experimental observation in the FQH state has remained elusive, making it a promising target for realization on current NISQ devices. In this work, we employ a quasi-one-dimensional model of an FQH state coupled to a background metric to probe the geometric response under a metric quench. We design and implement a quantum-circuit protocol that realizes a Hilbert-space-truncated version of the model and extracts the Hall viscosity from the geometric response encoded in the wavefunction dynamics of the device. While the truncation prevents us from accessing the fully quantized value of Hall viscosity, the hardware data nevertheless show excellent agreement with analytical and numerical predictions within this restricted regime. - oai:arXiv.org:2512.09982v1 + Higher-form entanglement asymmetry. Part I. The limits of symmetry breaking + https://arxiv.org/abs/2512.15898 + arXiv:2512.15898v1 Announce Type: cross +Abstract: Entanglement asymmetry is a relative entropy that faithfully diagnoses symmetry breaking in quantum states, possibly within a spatial subregion. In this work, we extend such framework to higher-form symmetries and compute entanglement asymmetry in theories with spontaneously-broken continuous zero- and higher-form symmetries. One of our central results is an entropic Coleman--Mermin--Wagner theorem, for $0$- and $p$-form symmetries, valid also on subregions, which forbids spontaneous breaking of continuous $p$-form symmetries in spacetime dimensions $d\leq p+2$. Our theorem not only qualifies symmetry breaking, it also quantifies it: spontaneous breaking triggers a nonvanishing entanglement asymmetry that grows monotonically towards the infrared, and counts the number of Goldstone fields. Along the way, we derive standalone results concerning the entanglement entropy of Goldstone bosons and gauge fields. + oai:arXiv.org:2512.15898v1 + hep-th + cond-mat.stat-mech cond-mat.str-el quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Francesco Benini, Eduardo Garc\'ia-Valdecasas, Stathis Vitouladitis + + + Tensor network approaches for plasma dynamics + https://arxiv.org/abs/2512.15924 + arXiv:2512.15924v1 Announce Type: cross +Abstract: The dynamics of plasmas are governed by a set of non-linear differential equations which remain challenging to solve directly for large 2D and 3D problems. Here we investigate how tensor networks could be applied to plasmas described by the Vlasov-Maxwell system of equations and investigate parameter regimes which show promise for efficient simulations. We show for low-dimensional problems that the simplest form of tensor networks known as a Matrix Product State performs sufficiently well, however in regimes with a strong permanent magnetic field or high-dimensional problems one may need to consider alternative tensor network geometries. We conclude the study of the Vlasov-Maxwell system with the application of tensor networks to an industrially relevant test case and validate our results against state of the art plasma solvers based on Particle-In-Cell codes. We also extend the application of tensor networks to the alternative plasma description of Magnetohydrodynamics and outline how this can be encoded using Matrix Product States. + oai:arXiv.org:2512.15924v1 + physics.plasm-ph + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ammar Kirmani, Andrew A. Allocca, Jian-Xin Zhu, Armin Rahmani, Sriram Ganeshan, Pouyan Ghaemi + Ryan J. J. Connor, Preetma Soin, Callum W. Duncan, Andrew J. Daley - Universal relaxation speedup in open quantum systems through transient conditional and unconditional resetting - https://arxiv.org/abs/2512.10005 - arXiv:2512.10005v1 Announce Type: cross -Abstract: Speeding up the relaxation dynamics of many-body quantum systems is important in a variety of contexts, including quantum computation and state preparation. We demonstrate that such acceleration can be universally achieved via transient stochastic resetting. This means that during an initial time interval of finite duration, the dynamics is interrupted by resets that take the system to a designated state at randomly selected times. We illustrate this idea for few-body open systems and also for a challenging many-body case, where a first-order phase transition leads to a divergence of relaxation time. In all scenarios, a significant and sometimes even exponential acceleration in reaching the stationary state is observed, similar to the so-called Mpemba effect. The universal nature of this speedup lies in the fact that the design of the resetting protocol only requires knowledge of a few macroscopic properties of the target state, such as the order parameter of the phase transition, while it does not necessitate any fine-tuned manipulation of the initial state. - oai:arXiv.org:2512.10005v1 - cond-mat.stat-mech + Full-field-of-view aberration correction for large arrays of focused beams + https://arxiv.org/abs/2512.15967 + arXiv:2512.15967v1 Announce Type: cross +Abstract: We propose and implement an aberration correction method for the creation of extended arrays of spots well beyond the isoplanatic region of any optical system. The method relies on an extensive calibration of aberrations in terms of Zernike polynomials over the full accessible field of an optical system. We introduce a modified Gerchberg-Saxton algorithm for generating holographic phase masks creating fully corrected arbitrary arrays of spots. By applying the method to an aspherical lens, and using a liquid-crystal spatial light modulator (SLM), we increase the aberration-free field of view from 50 to 500 $\mu$m, only limited by the largest diffraction angles accessible to the SLM. This opens new perspectives for the generation of large arrays of optical tweezers, especially for neutral atom based quantum processors and simulators. + oai:arXiv.org:2512.15967v1 + physics.optics quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross - http://creativecommons.org/licenses/by/4.0/ - Parvinder Solanki, Igor Lesanovsky, Gabriele Perfetto + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Yohann Machu, Gautier Creutzer, Cl\'ement Sayrin, Michel Brune - Entanglement in the Schwinger effect - https://arxiv.org/abs/2512.10091 - arXiv:2512.10091v1 Announce Type: cross -Abstract: We analyze entanglement generated by the Schwinger effect using a mode-by-mode formalism for scalar and spinor QED in constant backgrounds. Starting from thermal initial states, we derive compact, closed-form results for bipartite entanglement between particle-antiparticle partners in terms of the Bogoliubov coefficients. For bosons, thermal fluctuations enhance production but suppress quantum correlations: the logarithmic negativity is nonzero only below a (mode-dependent) critical temperature $T_c$. At fixed $T$, entanglement appears only above a critical field $E_{\text{crit,entang}}$. For fermions, we observe a qualitatively different pattern: at finite $T$ entanglement exists only within a finite window $E_{\text{min}} < E < E_{\text{max}}$, with a temperature-independent optimal field strength $E_{*}$ that maximizes the logarithmic negativity. Entanglement is vanishing above $T_{\text{max}}=\omega/\text{arcsinh}(1)$. We give quantitative estimates for analog experiments, where our entanglement criteria convert directly into concrete temperature and electric field constraints. These findings identify realistic regimes where the quantum character of Schwinger physics may be tested in the laboratory. - oai:arXiv.org:2512.10091v1 - hep-th - gr-qc + Optical coprocessor based on spontaneous Brillouin scattering + https://arxiv.org/abs/2512.15970 + arXiv:2512.15970v1 Announce Type: cross +Abstract: Analog coprocessors for neural networks are an intensively developing field. They provide approximate results of computations for relatively low energy cost and at high speed. We show that a set of ring resonators with Brillouin interaction between photons and phonons, being coupled to a waveguide, can be used to implement matrix-vector multiplication. The input vector is formed by occupancies of the anti-Stokes optical modes pumped via spontaneous Brillouin scattering, i.e, scattering on thermal phonons. Brillouin scattering rates and coupling constants between ring resonators and the waveguide form the matrix. The system allows for parallel computations in frequency band. + oai:arXiv.org:2512.15970v1 + physics.optics quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-nc-nd/4.0/ + I. V. Vovchenko, A. A. Zyablovsky, A. A. Pukhov, E. S. Andrianov + + + Magneto-optical Kerr effect in pump-probe setups + https://arxiv.org/abs/2512.16014 + arXiv:2512.16014v1 Announce Type: cross +Abstract: We develop a general theoretical framework for computing the time-resolved magneto-optical Kerr effect in ultrafast pump-probe setups, formulated within the Dynamical Projective Operatorial Approach (DPOA) and its application to the generalized linear-response theory for pumped systems. Furthermore, we exploit this formalism to express the post-pump optical conductivity and consequently the Kerr rotation in terms of the time-evolved single-particle density matrix (SPDM), providing a transparent and computationally efficient description of photo-excited multi-band systems. This extension, in addition to its lower computational cost, has the advantage of allowing the inclusion of phenomenological damping. We illustrate the formalism using both (i) a two-band tight-binding model, which captures the essential physics of ultrafast spin-charge dynamics and the Kerr rotation, and (ii) weakly spin-polarized germanium, as a realistic playground with a complex band structure. The results demonstrate that, by exploiting DPOA and/or its SPDM extension, one can reliably reproduce both the short-time features under the pump-pulse envelope and the long-time dynamics after excitation, offering a versatile framework for analyzing time-resolved magneto-optical Kerr effect experiments in complex materials. Moreover, this analysis clearly shows that the Kerr rotation can be used to deduce experimentally the relevant n-photon resonances for a given specific material. + oai:arXiv.org:2512.16014v1 + cond-mat.mtrl-sci + physics.optics + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Dimitrios Kranas, Amaury Marchon, Silvia Pla + Amir Eskandari-asl (Dipartimento di Fisica 'E.R. Caianiello', Universit\`a degli Studi di Salerno, Fisciano), Adolfo Avella (Dipartimento di Fisica 'E.R. Caianiello', Universit\`a degli Studi di Salerno, Fisciano) - Inflation is Not Magic - https://arxiv.org/abs/2512.10126 - arXiv:2512.10126v1 Announce Type: cross -Abstract: Cosmological perturbations generated during inflation exhibit striking quantum features, including entanglement and high circuit complexity. Yet their observational signatures remain effectively indistinguishable from classical stochastic variables. We quantify this tension by showing that quantum inflationary perturbations are continuous variable stabilizer states with vanishing quantum magic, a necessary resource for universal quantum computation as measured by Wigner negativity. Consequently, despite their quantum origins and description, these states can be efficiently simulated using classical algorithms. We further show that the Wigner negativity arising from primordial non-Gaussianity is suppressed not only by the non-linearity parameter $f_{NL}$, but also by the exponential squeezing of the perturbations. Viewing the early universe as a "high complexity, low magic" regime provides another perspective of what it means for the origin of structure in the universe to be "quantum." - oai:arXiv.org:2512.10126v1 - hep-th - gr-qc + Correlated many-body quantum dynamics of the Peregrine soliton + https://arxiv.org/abs/2512.16031 + arXiv:2512.16031v1 Announce Type: cross +Abstract: We explore the correlated dynamics underlying the formation of the quantum Peregrine soliton, a prototypical rogue-wave excitation, utilizing interaction quenches from repulsive to attractive couplings in an ultracold bosonic gas confined in a one-dimensional box trap. The latter emulates the so-called semi-classical initial conditions and the associated gradient catastrophe scenario facilitating the emergence of a high-density, doubly localized waveform. The ensuing multi-orbital variant of the Peregrine soliton features notable deviations from its mean-field sibling, including a reduced peak amplitude, wider core, absence of the side density dips, and earlier formation times. Moreover, Peregrine soliton generation yields coherence losses, while experiencing two-body bunching within each of its sides which show anti-bunching between each other. Controllable seeding of the Peregrine soliton is also demonstrated by tuning the atom number or the box length, while reducing the latter favors the generation of the time-periodic Kuznetsov-Ma breather. Our results highlight that correlations reshape the morphology of rogue-waves in the genuinely quantum, non-integrable realm, while setting the stage for the emergent field of quantum dispersive hydrodynamics. + oai:arXiv.org:2512.16031v1 + cond-mat.quant-gas + nlin.PS quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - S. Shajidul Haque, Ghadir Jafari, Bret Underwood + D. Diplaris, G. A. Bougas, P. G. Kevrekidis, C. -L. Hung, P. Schmelcher, S. I. Mistakidis - Approximate Counting in Local Lemma Regimes - https://arxiv.org/abs/2512.10134 - arXiv:2512.10134v1 Announce Type: cross -Abstract: We establish efficient approximate counting algorithms for several natural problems in local lemma regimes. In particular, we consider the probability of intersection of events and the dimension of intersection of subspaces. Our approach is based on the cluster expansion method. We obtain fully polynomial-time approximation schemes for both the probability of intersection and the dimension of intersection for commuting projectors. For general projectors, we provide two algorithms: a fully polynomial-time approximation scheme under a global inclusion-exclusion stability condition, and an efficient affine approximation under a spectral gap assumption. As corollaries of our results, we obtain efficient algorithms for approximating the number of satisfying assignments of conjunctive normal form formulae and the dimension of satisfying subspaces of quantum satisfiability formulae. - oai:arXiv.org:2512.10134v1 - cs.DS - math.CO - math.PR + Multi-messenger tracking of coherence loss during bond breaking + https://arxiv.org/abs/2512.16132 + arXiv:2512.16132v1 Announce Type: cross +Abstract: Coupled electronic and nuclear motions govern chemical reactions, yet disentangling their interplay during bond rupture remains challenging. Here we follow the light-induced fragmentation of Br$_2$ using a coincidence-based multi-messenger approach. A UV pulse prepares the dissociative state, and strong-field ionization probes the evolving system. Coincident measurement of three-dimensional photoion and photoelectron momenta provides real-time access to both the instantaneous internuclear separation and the accompanying reorganization of the electronic structure, allowing us to determine the timescale of bond breaking. We find that electronic rearrangement concludes well before the nuclei reach the bond-breaking distance, revealing a hierarchy imposed by electron-nuclear coupling. Supported by semiclassical modelling, the results show that the stretched Br$_2$ molecule behaves as a two-centre interferometer in which the loss of coherence between atomic centres encodes the coupled evolution of electrons and nuclei. Our work establishes a general framework for imaging ultrafast electron-nuclear dynamics in molecules. + oai:arXiv.org:2512.16132v1 + physics.chem-ph + physics.atom-ph + physics.optics quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ryan L. Mann, Gabriel Waite + Tian Wang, Nida Haram, Zack Dube, Kyle A. Hamer, Yonghao Mi, Fatemeh Karimi, Andrei Yu. Naumov, Giulio Vampa, Caterina Vozzi, Xiaojun Liu, Albert Stolow, Michael Schuurman, Nicolas Douguet, David Villeneuve, Paul B. Corkum, Andre Staudte - Search for a solar-bound axion halo using the Global Network of Optical Magnetometers for Exotic physics searches - https://arxiv.org/abs/2512.10221 - arXiv:2512.10221v1 Announce Type: cross -Abstract: We report on a search for a gravitationally bound solar axion halo using data from the Global Network of Optical Magnetometers for Exotic physics searches (GNOME), a worldwide array of magnetically shielded atomic magnetometers with sensitivity to exotic spin couplings. Motivated by recent theoretical work suggesting that self-interacting ultralight axions can be captured by the Sun's gravitational field and thermalize into the ground state, we develop a signal model for the pseudo-magnetic fields generated by axion-proton gradient couplings in such a halo. The analysis focuses on the fifth GNOME Science Run (69 days, 12 stations), employing a cross-correlation pipeline with time-shifted daily modulation templates to search for the global, direction-dependent, monochromatic signal expected from a solar axion halo. No statistically significant candidate signals are observed. We set 95% confidence-level upper limits on the amplitude of the axion-induced pseudo-magnetic field over the frequency range 0.05 Hz to 20 Hz, translating to constraints on the linear and quadratic axion-proton couplings for halo densities predicted by gravitational capture models and for the maximum overdensities allowed by planetary ephemerides. In the quadratic coupling case, our limits surpass existing astrophysical bounds by over two orders of magnitude across much of the accessible parameter space. - oai:arXiv.org:2512.10221v1 - physics.atom-ph + Quantum Readiness in Latin American High Schools: Curriculum Compatibility and Enabling Conditions + https://arxiv.org/abs/2512.16257 + arXiv:2512.16257v1 Announce Type: cross +Abstract: The accelerating global development of quantum technologies strengthens the case for introducing quantum computing concepts before university. Yet in Latin America, there is no consolidated, region wide integration of quantum computing into secondary education, and the feasibility conditions for doing so remain largely unexamined. This paper proposes a qualitative, comparative framework to assess academic readiness for quantum education across six countries - Peru, Bolivia, Chile, Argentina, Brazil, and Colombia - grounded in the relationship between curriculum compatibility and enabling conditions spanning institutional capacity, teacher preparation, infrastructure, and equity. Using official curricula, policy documents, national statistics, and educational reports, we apply structured qualitative coding and a 1-5 ordinal scoring system to generate a cross country diagnosis. The findings reveal substantial regional asymmetries: among the six countries studied, Chile emerges as the most institutionally prepared for progressive quantum education integration, while the remaining countries exhibit varying combinations of curricular gaps and fragmented but promising enabling conditions. Building on this diagnosis, we propose a country sensitive, regionally coordinated roadmap for staged implementation, beginning with teacher development and pilot centers, leveraging open source platforms and local language resources, and scaling toward gradual curricular integration. This work establishes a baseline for future quantitative and mixed method studies evaluating learning outcomes, motivation, and scalable models for quantum education in Latin America. + oai:arXiv.org:2512.16257v1 + physics.ed-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Adriana Celeste Alvarado Leon, Osmar Denilson Herrera Cueva, Rosario Mercedes Morales Orvezo, Daniella Alexandra Crysti Vargas Saldana, Freddy Herrera Cueva + + + Neutrino Propagation in Quantum Field Theory at Short and Long Baselines + https://arxiv.org/abs/2512.16281 + arXiv:2512.16281v1 Announce Type: cross +Abstract: In a quantum field approach to neutrino oscillations, the neutrino is treated as a propagator, while the external initial and final particle states are described by covariant wave packets. For the asymptotic behavior on short and long macroscopic baselines, the wave packet modified neutrino propagator is expressed through asymptotic series in powers of dimensionless Lorentz and rotation invariant variables. In both regimes, leading-order corrections violate the classical inverse-square law and lead to a decrease in the neutrino-induced event rate. The possibility that the so-called reactor antineutrino anomaly can, at least partially, be explained within this approach is discussed. + oai:arXiv.org:2512.16281v1 + hep-ph + hep-th + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Tatum Z. Wilson, Derek F. Jackson Kimball, Samer Afach, Jiexiao Bi, B. C. Buchler, Dmitry Budker, Kaleb Cervantes, Joshua Eby, Nataniel L. Figueroa, Ron Folman, Jiawei Gao, Daniel Gavil\'an-Mart\'in, Menachem Givon, Zoran D. Gruji\'c, Hong Guo, Paul Hamilton, M. P. Hedges, Zhejun Huang, Dongok Kim, Younggeun Kim, Sami S. Khamis, Emmanuel Klinger, Abaz Kryemadhi, Nina Kukowski, Jianjun Li, Grzegorz Lukasiewicz, Hector Masia-Roig, Michal Padniuk, Christopher A. Palm, Chaitanya Paranjape, Sun Yool Park, Xiang Peng, Gilad Perez, Rayshaun Preston, Szymon Pustelny, Wolfram Ratzinger, Yossi Rosenzweig, Ophir M. Ruimi, Amy Saputo, Theo Scholtes, P. C. Segura, Yannis K. Semertzidis, Yun Chang Shin, Jason E. Stalnaker, Ibrahim Sulai, Dhruv Tandon, Ken Vu, Arne Wickenbrock, Teng Wu, Yucheng Yang, Yixin Zhao + Vadim A. Naumov, Dmitry S. Shkirmanov - Excitation energies and UV-Vis absorption spectra from INDO/s+ML - https://arxiv.org/abs/2512.10397 - arXiv:2512.10397v1 Announce Type: cross -Abstract: The semi-empirical INDO/s method is popular for studies of excitation energies and absorption of molecules due to its low computational requirement, making it possible to make predictions for large systems. However, its accuracy is generally low, particularly, when compared with the typical accuracy of other methods such as time-dependent density functional theory (TDDFT). Here, we present machine learning (ML) models that correct the INDO/s results with negligible increases in the amount of computing resources needed. While INDO/s excitations energies have an average error of about 1.1 eV relative to TDDFT energies, the added ML corrections reduce the error to 0.2 eV. Furthermore, this combination of INDO/s and ML produces UV-Vis absorption spectra that are in good agreement with the TDDFT predictions. - oai:arXiv.org:2512.10397v1 - cond-mat.mes-hall - physics.atm-clus - physics.chem-ph - physics.comp-ph + Entropy of Schwinger pair production in time-dependent Sauter pulse electric field + https://arxiv.org/abs/2512.16328 + arXiv:2512.16328v1 Announce Type: cross +Abstract: We investigate entropy of electron-positron pair production in time-dependent Sauter pulse electric field. Both cases of pair longitudinal momentum only and full momentum consideration are examined. We further examine three types of entropy, one is the usual entanglement entropy $S_{\text{E}}$, the other two extensions are thermal distribution entropy $S_{\text{Th}}$, and that with the chemical potential correction, $S_{\text{Th,CP}}$. For short pulse, $S_{\text{E}}$ is higher than $S_{\text{Th}}$ and vice versa for long pulse. The chemical potential causes the single-particle average thermal distribution entropy $\frac{S_{\text{Th,CP}}}{N}$ to exhibit non-monotonic behavior, similar to the single-particle average entanglement entropy $\frac{S_{\text{E}}}{N}$ in the short-pulse range. In the full momentum case, we calculate the thermal distribution entropy $S_{\text{Th, U}}$ via introducing the Unruh temperature as the local effective temperature. We find that both $S_{\text{Th, U}}$ and $S_{\text{E}}$ saturate asymptotically to the constant while the former has a larger asymptotic value. The results presented in this study reveals that the different entropies have some delicate relationships among them. + oai:arXiv.org:2512.16328v1 + hep-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ezekiel Oyeniyi, Omololu Akin-Ojo + http://creativecommons.org/licenses/by/4.0/ + Zhi-Hang Yao, Hong-Hao Fan, Lie-Juan Li, Hai-Bo Sang, Bai-Song Xie - Entanglement in C$^*$-algebras: tensor products of state spaces - https://arxiv.org/abs/2512.10410 - arXiv:2512.10410v1 Announce Type: cross -Abstract: We analyze the Namioka-Phelps minimal and maximal tensor products of compact convex sets arising as state spaces of C$^*$-algebras, and, relatedly, study entanglement in (infinite dimensional) C$^*$-algebras. The minimal Namioka-Phelps tensor product of the state spaces of two C$^*$-algebras is shown to correspond to the set of separable (= un-entangled) states on the tensor product of the C$^*$-algebras. We show that these maximal and minimal tensor product of the state spaces agree precisely when one of the two C$^*$-algebras is commutative. This confirms an old conjecture by Barker in the case where the compact convex sets are state spaces of C$^*$-algebras. - The Namioka-Phelps tensor product of the trace simplexes of two C$^*$-algebras is shown always to be the trace simplex of the tensor product of the C$^*$-algebras. This can be used, for example, to show that the trace simplex of (any) tensor product of two C$^*$-algebras is the Poulsen simplex if and only if the trace simplex of each of the C$^*$-algebras is the Poulsen simplex. - oai:arXiv.org:2512.10410v1 - math.OA - math.FA + Photoacoustic model for laser-induced acoustic desorption of nanoparticles + https://arxiv.org/abs/2512.16403 + arXiv:2512.16403v1 Announce Type: cross +Abstract: Laser-induced acoustic desorption (LIAD) enables loading nanoparticles into optical traps under vacuum for levitated optomechanics experiments. Current LIAD systems rely on empirical optimization using available laboratory lasers rather than systematic theoretical design, resulting in large systems incompatible with portable or space-based applications. We develop a theoretical framework using the photoacoustic wave equation to model acoustic wave generation and propagation in metal substrates, enabling systematic optimization of laser parameters. The model identifies key scaling relationships: surface acceleration scales as $\tau^{-2}$ with pulse duration, while acoustic diffraction sets fundamental limits on optimal spot size $w \gtrsim \sqrt{v\tau d}$. Material figures of merit combine thermal expansion and optical absorption properties, suggesting alternatives to traditional aluminum substrates. The framework validates well against experimental data and demonstrates that compact laser systems with sub-nanosecond pulse durations can achieve performance competitive with existing laboratory-scale implementations despite orders-of-magnitude lower pulse energies. This enables rational design of minimal LIAD systems for practical applications. + oai:arXiv.org:2512.16403v1 + physics.optics quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Magdalena Musat, Mikael R{\o}rdam + Matthew Edmonds, James Bateman - Rapid all-optical loading of trapped ions using a miniaturised atom source - https://arxiv.org/abs/2512.10514 - arXiv:2512.10514v1 Announce Type: cross -Abstract: We characterise an efficient optically-heated neutral atom source for ion trapping. We observe loading rates of up to $24(3)\,\mathrm{s}^{-1}$ with heating powers below $85\,\mathrm{mW}$, and demonstrate loading of a single ion in under $30\,\mathrm{s}$ with $41.4(4)\,\mathrm{mW}$ of optical power in a room-temperature ion trap system with an ionisation probability of $1.50(5)\times10^{-5}$. We calibrate a thermal model for the source's internal temperature by imaging the fluorescence of a collimated flux of neutral calcium that effuses from the oven at various optical heating powers. We show that the thermal performance of this oven is mainly limited by radiative losses. We explore the effect of second-stage photo-ionisation laser power on the loading rate, and identify a path beyond the loading rates reported in this study. We predict that this source is also well-suited to a wide range of metals used in ion-trapping. - oai:arXiv.org:2512.10514v1 - physics.atom-ph + Rationally-extended radial harmonic oscillator in a position-dependent mass background + https://arxiv.org/abs/2512.16510 + arXiv:2512.16510v1 Announce Type: cross +Abstract: We show that the radial harmonic oscillator problem in the position-dependent mass background of the type $m(\alpha;r) = (1+\alpha r^2)^{-2}$, $\alpha>0$, can be solved by using a point canonical transformation mapping the corresponding Schr\"odinger equation onto that of the P\"oschl-Teller I potential with constant mass. The radial harmonic oscillator problem with position-dependent mass is shown to exhibit a deformed shape invariance property in a deformed supersymmetric framework. The inverse point canonical transformation then provides some exactly-solvable rational extensions of the radial harmonic oscillator with position-dependent mass associated with $X_m$-Jacobi exceptional orthogonal polynomials of type I, II, or III. The extended potentials of type I and II are proved to display deformed shape invariance. The spectrum and wavefunctions of the radial harmonic oscillator potential and its extensions are shown to go over to well-known results when the deforming parameter $\alpha$ goes to zero. + oai:arXiv.org:2512.16510v1 + math-ph + math.MP + nlin.SI quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Lorenzo Versini, Tim F. Wohlers-Reichel, Catherine E. J. Challoner, Thomas Hinde, Arjun D. Rao, William J. Hughes, Peter Drmota, Thomas H. Doherty, Laurent J. Stephenson, Jacob A. Blackmore, Joseph F. Goodwin + Christiane Quesne - Edge states of a Bi$_2$Se$_3$ nanosheet in a perpendicular magnetic field - https://arxiv.org/abs/2512.10627 - arXiv:2512.10627v1 Announce Type: cross -Abstract: Conventional wisdom dictates that the conducting edge states of two-dimensional topological insulators of the Bi$_2$Se$_3$ family are protected by time-reversal symmetry. However, theoretical bulk calculations and a recent experiment show that the edge states persist in the presence of large external magnetic fields. To address this apparent contradiction, we have developed an analytical description for the edge-state wave function of a semi-infinite sample in a perpendicular magnetic field. Our description relies on the usual bulk Landau levels, together with additional states arising due to the presence of the hard wall, which are unnormalizable in the infinite system. The analytical wave functions agree extremely well with numerical calculations and can be used to directly analyze the behavior of the edge states in a magnetic field. - oai:arXiv.org:2512.10627v1 - cond-mat.mes-hall - cond-mat.mtrl-sci + Landscape Analysis of Excited States Calculation over Quantum Computers + https://arxiv.org/abs/2512.16539 + arXiv:2512.16539v1 Announce Type: cross +Abstract: The variational quantum eigensolver (VQE) is one of the most promising algorithms for low-lying eigenstates calculation on Noisy Intermediate-Scale Quantum (NISQ) computers. Specifically, VQE has achieved great success for ground state calculations of a Hamiltonian. However, excited state calculations arising in quantum chemistry and condensed matter often requires solving more challenging problems than the ground state as these states are generally further away from a mean-field description, and involve less straightforward optimization to avoid the variational collapse to the ground state. Maintaining orthogonality between low-lying eigenstates is a key algorithmic hurdle. In this work, we analyze three VQE models that embed orthogonality constraints through specially designed cost functions, avoiding the need for external enforcement of orthogonality between states. Notably, these formulations possess the desirable property that any local minimum is also a global minimum, helping address optimization difficulties. We conduct rigorous landscape analyses of the models' stationary points and local minimizers, theoretically guaranteeing their favorable properties and providing analytical tools applicable to broader VQE methods. A comprehensive comparison between the three models is also provided, considering their quantum resource requirements and classical optimization complexity. + oai:arXiv.org:2512.16539v1 + math.NA + cs.NA quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stan P. J. Koenis, Lucas Maisel Licer\'an, Henk T. C. Stoof + Hengzhun Chen, Yingzhou Li, Bichen Lu, Jianfeng Lu - Phase structure of the one-dimensional $\mathbb{Z}_2$ lattice gauge theory with second nearest-neighbor interactions - https://arxiv.org/abs/2512.10755 - arXiv:2512.10755v1 Announce Type: cross -Abstract: We investigate the ground-state phase diagram of a one-dimensional $\mathbb{Z}_2$ lattice gauge theory (LGT) model with hard-core bosons at half-filling, extending previous studies by including second nearest-neighbor (2NN) interactions. Using matrix product state techniques within the density matrix renormalization group, we compute charge gap, static structure factor, and pair-pair correlation functions for various interaction strengths and field parameters. We analyze two representative neatest-neighbor interaction strengths ($V_1$) that correspond to the Luttinger liquid (LL) and Mott insulator (MI) phases in the absence of the 2NN interactions. We introduce the 2NN coupling $V_2$ and investigate its impact on the system. Our results reveal very rich behavior. As the 2NN repulsion increases, in the case of small $V_1$, we observe a direct transition from the LL phase to a charge-ordered insulator (COI) phase, whereas for large $V_1$, we observe a transition from the MI phase (previously found with only $V_1$ included), going through an intermediate LL region, and finally reaching the COI regime. Additionally, the inclusion of 2NN interactions enhances charge order and suppresses pair coherence, evidenced by sharp peaks in the structure factor and rapid decay in pair-pair correlators. Our work extends the well-studied phase structure of 1D $\mathbb{Z}_2$ LGT models and demonstrates the interplay between gauge fields, confinement, and extended interactions. - oai:arXiv.org:2512.10755v1 - cond-mat.str-el - hep-lat + Condensation of slow $\gamma$-quanta in strong magnetic fields + https://arxiv.org/abs/2512.16628 + arXiv:2512.16628v1 Announce Type: cross +Abstract: The implications of the root singularity of the vacuum polarization tensor near the first pair creation threshold on blackbody radiation are investigated for magnetic fields above the characteristic scale of quantum electrodynamics. We show that the vacuum birefringence in such a strong background leads to an anisotropic behavior of the Planck radiation law. The thermal spectrum is characterized by a resonance that competes with the Wien maximum, causing a crossover in the low $\gamma$-spectrum of the heat radiation. A light state resembling a many-body condensate with slow motion is linked to the high-temperature phase. This novel state of radiation may coexist with nuclear or quark matter in a neutron star's core, increasing its compactness and influencing its stability. + oai:arXiv.org:2512.16628v1 hep-ph - physics.comp-ph + cond-mat.other quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yeimer Zambrano, Aleksey Alekseev, Konrad J. Kapcia, Krzysztof Cichy, Agnieszka Cichy + Leah Folkerts, Reinhold Egger, Carsten M\"uller, Selym Villalba-Ch\'avez - Metrics on completely positive maps via noncommutative geometry - https://arxiv.org/abs/2512.10842 - arXiv:2512.10842v1 Announce Type: cross -Abstract: By considering an infinite-dimensional analogue of the Choi-Jamiolkowski isomorphism, we study how to induce metrics on a distinguished subset of the completely positive maps between tracial $C^*$-algebras using seminorms from noncommutative geometry. Under suitable conditions on the these seminorms, we show that the induced metrics will satisfy the quantum information theoretic properties of stability and chaining. Lastly, we show how to generate such metrics from Kasparov exterior products of spectral triples. - oai:arXiv.org:2512.10842v1 - math.OA - math.FA + Explicit finite-time illustration of improper unitary evolution for the Klein--Gordon field in de Sitter space + https://arxiv.org/abs/2512.16666 + arXiv:2512.16666v1 Announce Type: cross +Abstract: It is known that quantum field theories in curved spacetime suffer from a number of pathologies, including the inability to relate states on different spatial slices by proper unitary time-evolution operators. In this article, we illustrate this issue by describing the canonical quantisation of a free scalar field in de Sitter space and explicitly demonstrating that the vacuum at a given time slice is unitarily inequivalent to that at any other time. In particular, we find that, if both background and Hamiltonian dynamics are taken into account, this inequivalence holds even for infinitesimally small time steps and not only in the asymptotic time limits. + oai:arXiv.org:2512.16666v1 + hep-th + gr-qc + hep-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Are Austad, Erik B\'edos, Jonas Eidesen, Nadia S. Larsen, Tron Omland + William T. Emond, Christian K\"ading, Peter Millington - Hybrid quantum-classical matrix-product state and Lanczos methods for electron-phonon systems with strong electronic correlations: Application to disordered systems coupled to Einstein phonons - https://arxiv.org/abs/2512.10899 - arXiv:2512.10899v1 Announce Type: cross -Abstract: We present two quantum-classical hybrid methods for simulating the time-dependence of electron-phonon systems that treat electronic correlations numerically exactly and optical-phonon degrees of freedom classically. These are a time-dependent Lanczos and a matrix-product state method, each combined with the multi-trajectory Ehrenfest approach. Due to the approximations, reliable results are expected for the adiabatic regime of small phonon frequencies. We discuss the convergence properties of both methods for a system of interacting spinless fermions in one dimension and provide a benchmark for the Holstein chain. As a first application, we study the decay of charge density wave order in a system of interacting spinless fermions coupled to Einstein oscillators and in the presence of quenched disorder. We investigate the dependence of the relaxation dynamics on the electron-phonon coupling strength and provide numerical evidence that the coupling of strongly disordered systems to classical oscillators leads to delocalization, thus destabilizing the (finite-size) many-body localization in this system. - oai:arXiv.org:2512.10899v1 - cond-mat.str-el - cond-mat.dis-nn + Field Quantisations in Schwarzschild Spacetime: Theory versus Low-Energy Experiments + https://arxiv.org/abs/2512.16667 + arXiv:2512.16667v1 Announce Type: cross +Abstract: Non-relativistic quantum particles in the Earth's gravitational field are successfully described by the Schr\"{o}dinger equation with Newton's gravitational potential. Particularly, quantum mechanics is in agreement with such experiments as free fall and quantum interference induced by gravity. However, quantum mechanics is a low-energy approximation to quantum field theory. The latter is successful by the description of high-energy experiments. Gravity is embedded in quantum field theory through the general-covariance principle. This framework is known in the literature as quantum field theory in curved spacetime, where the concept of a quantum particle is, though, ambiguous. In this article, we study in this framework how a Hawking particle moves in the far-horizon region of Schwarzschild spacetime by computing its propagator. We find this propagator differs from that which follows from the path-integral formalism -- the formalism which adequately describes both free fall and quantum interference induced by gravity. + oai:arXiv.org:2512.16667v1 + gr-qc + hep-th quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Heiko Georg Menzler, Suman Mondal, Fabian Heidrich-Meisner + http://creativecommons.org/licenses/by/4.0/ + Viacheslav A. Emelyanov - Rapid multi-mode trapped-ion laser cooling in a phase-stable standing wave - https://arxiv.org/abs/2512.10900 - arXiv:2512.10900v1 Announce Type: cross -Abstract: Laser cooling is fundamental to precise control and interrogation of atomic quantum systems. In the context of quantum computing and metrology with trapped ions, the integrated optical control of interest for scaling may additionally enable increased performance of coherent and incoherent operations. Here we utilize multi-channel integrated delivery of ultraviolet to infrared wavelengths required for calcium ion control including in passively phase-stable ultraviolet standing waves to demonstrate rapid, broadband laser cooling. We experimentally verify a long-standing prediction, realizing Doppler cooling to below the conventional Doppler limit at a standing-wave (SW) node. Utilizing electromagnetically induced transparency (EIT), we experimentally cool motional modes spanning an approximately 5 MHz bandwidth from the Doppler temperature to near the ground state within 150 $\mu$s, reaching $\bar n \approx 0.05$ phonon number occupancies for the target mode. Direct evaluation against the comparable running-wave (RW) scheme shows the SW implementation's simultaneous advantage in cooling rate, motional mode bandwidth, and final phonon number as previously theoretically predicted. Our results demonstrate structured light's capability for robust ground-state laser cooling, and a clear advantage in a fundamental functionality enabled by scalable approaches to optical control. - oai:arXiv.org:2512.10900v1 - physics.atom-ph + Model-Based Real-Time Synthesis of Acousto-Optically Generated Laser-Beam Patterns and Tweezer Arrays + https://arxiv.org/abs/2512.16774 + arXiv:2512.16774v1 Announce Type: cross +Abstract: Acousto-optic deflectors (AOD) enable spatiotemporal control of laser beams through diffraction at an ultrasonic grating that is controllable by radio-frequency (rf) waveforms. These devices are a widely used tool for high-bandwidth random-access scanning applications, such as optical tweezers in quantum technology. A single AOD can generate multiple optical tweezers by multitone rf input in one dimension. Two-dimensional (2D) patterns can be realized with two perpendicularly oriented AODs. As the acousto-optical response depends nonlinearly on the applied frequency components, phases, and amplitudes, and in addition experiences dimensional coupling in 2D setups, intensity regulation becomes a unique challenge. Guided by coupled-wave theory and experimental observations, we derive a compute-efficient model which we implement on a graphics processing unit. Only one-time sampling of single-tone laser-power calibration is needed for model parameter determination, allowing for straight-forward integration into optical instruments. We implement and experimentally validate an open-loop diffraction efficiency control system that enables programmable 2D multibeam trajectories with intensity control applied at every time step during digital signal generation, overcoming the limited flexibility, pattern-size constraints, and bandwidth limitations of methods using precalculation and precalibration of a predefined pattern set or closed-loop feedback. The system is capable of stable real-time waveform streaming of arrays with up to 50 x 50 tweezers with minimal time resolution of 1.4 ns (700 MS/s) and a peak latency below 257 microseconds for execution of newly requested patterns. Reactive, real-time 2D multibeam laser patterning and scanning with strict intensity matching will substantially benefit parallelization and increasing data rates in materials processing, microscopy, and optical tweezers. + oai:arXiv.org:2512.16774v1 physics.optics quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zhenzhong Xing, Hamim Mahmud Rivy, Vighnesh Natarajan, Aditya Milind Kolhatkar, Gillenhaal Beck, Karan K. Mehta + 10.1103/d3tx-3tg8 + Phys. Rev. Appl. vol.24, 064046 (2025) + Marcel Mittenbuehler, Lukas Sturm, Malte Schlosser, Gerhard Birkl - Twin-paradox and Entanglement - https://arxiv.org/abs/2512.10908 - arXiv:2512.10908v1 Announce Type: cross -Abstract: We study the quantum version of the classical twin paradox in special relativity by replacing the twins with quantum detectors, and studying the transitions and entanglement induced by coupling them to a quantum field. We show that the \textit{changes} in direction of acceleration leave imprints on detector responses and entanglement, inducing novel features which might have relevance in black hole spacetimes. - oai:arXiv.org:2512.10908v1 - gr-qc + Revival Dynamics from Equilibrium States: Scars from Chords in SYK + https://arxiv.org/abs/2512.16836 + arXiv:2512.16836v1 Announce Type: cross +Abstract: We develop a novel framework to build quantum many-body scar states in bipartite systems characterized by perfect correlation between the Hamiltonians governing the two sides. By means of a Krylov construction, we build an interaction term which supports a tower of equally-spaced energy eigenstates. This gives rise to finite-time revivals whenever the system is initialized in a purification of a generic equilibrium state. The dynamics is universally characterized, and is largely independent of the specific details of the Hamiltonians defining the individual partitions. By considering the two-sided chord states of the double-scaled SYK model, we find an approximate realization of this framework. We analytically study the revival dynamics, finding rigid motion for wavepackets localized on the spectrum of a single SYK copy. These findings are tested numerically for systems of finite size, showing excellent agreement with the analytical predictions. + oai:arXiv.org:2512.16836v1 + cond-mat.str-el hep-th quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - K. Hari, Subhajit Barman, Dawood Kothawala + Debarghya Chakraborty, Dario Rosa - Electronic crystals and quasicrystals in semiconductor quantum wells: an AI-powered discovery - https://arxiv.org/abs/2512.10909 - arXiv:2512.10909v1 Announce Type: cross -Abstract: The homogeneous electron gas is a cornerstone of quantum condensed matter physics, providing the foundation for developing density functional theory and understanding electronic phases in semiconductors. However, theoretical understanding of strongly-correlated electrons in realistic semiconductor systems remains limited. In this work, we develop a neural network based variational approach to study quantum wells in three dimensional geometry for a variety of electron densities and well thicknesses. Starting from first principles, our unbiased AI-powered method reveals metallic and crystalline phases with both monolayer and bilayer charge distributions. In the emergent bilayer, we discover a new quantum phase of matter: the electronic quasicrystal. - oai:arXiv.org:2512.10909v1 - cond-mat.str-el + Signatures of real-space geometry, topology, and metric tensor in quantum transport in periodically corrugated spaces + https://arxiv.org/abs/2512.16846 + arXiv:2512.16846v1 Announce Type: cross +Abstract: The motion of a quantum particle constrained to a two-dimensional non-compact Riemannian manifold with non-trivial metric can be described by a flat-space Schroedinger-type equation at the cost of introducing local mass and metric and geometry-induced effective potential with no classical counterpart. For a metric tensor periodically modulated along one dimension, the formation of bands is demonstrated and transport-related quantities are derived. Using S-matrix approach, the quantum conductance along the manifold is calculated and contrasted with conventional quantum transport methods in flat spaces. The topology, e.g. whether the manifold is simply connected, compact or non-compact shows up in global, non-local properties such as the Aharonov-Bohm phase. The results vividly demonstrate emergent phenomena due to the interplay of reduced-dimensionality, particles quantum nature, geometry, and topology. + oai:arXiv.org:2512.16846v1 cond-mat.mes-hall + math-ph + math.MP + physics.class-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross - http://creativecommons.org/licenses/by/4.0/ - Filippo Gaggioli, Pierre-Antoine Graham, Liang Fu + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Benjamin Schwager, Theresa Appel, Jamal Berakdar - On Decision-Making Agents and Higher-Order Causal Processes - https://arxiv.org/abs/2512.10937 - arXiv:2512.10937v1 Announce Type: cross -Abstract: We establish a precise correspondence between decision-making agents in partially observable Markov decision processes (POMDPs) and one-input process functions, the classical limit of higher-order quantum operations. In this identification an agent's policy and memory update combine into a process function w that interacts with a POMDP environment via the link product. This suggests a dual interpretation: in the physics view, the process function acts as the environment into which local operations (agent interventions) are inserted, whereas in the AI view it encodes the agent and the inserted functions represent environments. We extend this perspective to multi-agent systems by identifying observation-independent decentralized POMDPs as natural domains for multi-input process functions. - oai:arXiv.org:2512.10937v1 - cs.AI + Electric field diagnostics in a continuous rf plasma using Rydberg-EIT + https://arxiv.org/abs/2512.16867 + arXiv:2512.16867v1 Announce Type: cross +Abstract: We present a non-invasive spectroscopic technique to measure electric fields in plasma, leveraging large polarizabilities and Stark shifts of Rydberg atoms. Rydberg Stark shifts are measured with high precision using narrow-linewidth lasers via Electromagnetically Induced Transparency (EIT) of rubidium vapor seeded into a continuous, inductively coupled radio-frequency (rf) plasma in a few mTorr of argon gas. Without plasma, the Rydberg-EIT spectra exhibit rf modulation sidebands caused by electric- and magnetic-dipole transitions in the rf drive coil. With the plasma present, the rf modulation sidebands vanish due to screening of the rf drive field from the plasma interior. The lineshapes of the EIT spectra in the plasma reflect the plasma's Holtsmark microfield distribution, allowing us to determine plasma density and collisional line broadening over a range of pressures and rf drive powers. The work is expected to have applications in non-invasive spatio-temporal electric-field diagnostics of low-pressure plasma, plasma sheaths, process plasma and dusty plasma. + oai:arXiv.org:2512.16867v1 + physics.atom-ph + physics.plasm-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Matt Wilson + Bineet Dash, Xinyan Xiang, Dingkun Feng, Eric Paradis, Georg Raithel - Performance Analysis of Quantum CSS Error-Correcting Codes via MacWilliams Identities - https://arxiv.org/abs/2305.01301 - arXiv:2305.01301v4 Announce Type: replace -Abstract: We analyze the performance of quantum stabilizer codes, one of the most important classes for practical implementations, on both symmetric and asymmetric quantum channels. To this aim, we first derive the weight enumerator (WE) for the undetectable errors based on the quantum MacWilliams identities. The WE is then used to evaluate tight upper bounds on the error rate of CSS quantum codes with \acl{MW} decoding. For surface codes we also derive a simple closed form expression of the bounds over the depolarizing channel. We introduce a novel approach that combines the knowledge of WE with a logical operator analysis, allowing the derivation of the exact asymptotic error rate for short codes. For example, on a depolarizing channel with physical error rate $\rho \to 0$, the logical error rate $\rho_\mathrm{L}$ is asymptotically $\rho_\mathrm{L} \approx 16 \rho^2$ for the $[[9,1,3]]$ Shor code, $\rho_\mathrm{L} \approx 16.3 \rho^2$ for the $[[7,1,3]]$ Steane code, $\rho_\mathrm{L} \approx 18.7 \rho^2$ for the $[[13,1,3]]$ surface code, and $\rho_\mathrm{L} \approx 149.3 \rho^3$ for the $[[41,1,5]]$ surface code. For larger codes our bound provides $\rho_\mathrm{L} \approx 1215 \rho^4$ and $\rho_\mathrm{L} \approx 663 \rho^5$ for the $[[85,1,7]]$ and the $[[181,1,10]]$ surface codes, respectively. Finally, we extend our analysis to include realistic, noisy syndrome extraction circuits by modeling error propagation throughout gadgets. This enables estimation of logical error rates under faulty measurements. The performance analysis serves as a design tool for developing fault-tolerant quantum systems by guiding the selection of quantum codes based on their error correction capability. Additionally, it offers a novel perspective on quantum degeneracy, showing it represents the fraction of non-correctable error patterns shared by multiple logical operators. - oai:arXiv.org:2305.01301v4 + Fighting non-locality with non-locality: microcausality and boundary conditions in QED + https://arxiv.org/abs/2512.16898 + arXiv:2512.16898v1 Announce Type: cross +Abstract: In gauge theories, globally charged observables necessarily depend non-locally on the kinematical fields, with this dependence extending to the asymptotic boundary of spacetime. Despite this, we show that a subset of such observables can be consistently regarded as local to the bulk, in a manner that respects microcausality and leaves locality properties of uncharged observables untouched. A sufficient condition for this is to impose kinematically non-local boundary conditions on the large gauge sector of the theory, and to invoke a relational notion of localisation for observables. This reveals a relatively underappreciated link between boundary conditions, and different notions of microcausality and locality. We develop this point through a detailed case study in scalar QED, describing non-local boundary conditions that allow a large family of observables on a codimension-1 bulk surface to be viewed as local to that surface, despite being dressed by asymptotic Wilson lines. We show that this property continues to hold within a perturbative quantisation of the theory, and we argue that this leads to a consistent local net of algebras that includes these charged observables in bulk algebras. We explain how this setup may be understood in terms of a preferred dynamical reference frame for small gauge transformations appearing in the boundary conditions. Many features of the theory (such as microcausality, the vacuum state, and the net of algebras of observables) depend on the choice of this frame, and we briefly discuss some repercussions of this for algebraic formulations of QFT. While our analysis is performed in QED, we expect our results to carry over qualitatively to more complicated theories including gravity. + oai:arXiv.org:2512.16898v1 + hep-th + gr-qc quant-ph - cs.IT - math.IT - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Philipp A. Hoehn, Josh Kirklin + + + Current fluctuations in open quantum systems: Bridging the gap between quantum continuous measurements and full counting statistics + https://arxiv.org/abs/2303.04270 + arXiv:2303.04270v5 Announce Type: replace +Abstract: Continuously measured quantum systems are characterized by an output current, in the form of a stochastic and correlated time series which conveys crucial information about the underlying quantum system. The many tools used to describe current fluctuations are scattered across different communities: quantum opticians often use stochastic master equations, while a prevalent approach in condensed matter physics is provided by full counting statistics. These, however, are simply different sides of the same coin. Our goal with this tutorial is to provide a unified toolbox for describing current fluctuations. This not only provides novel insights, by bringing together different fields in physics, but also yields various analytical and numerical tools for computing quantities of interest. We illustrate our results with various pedagogical examples, and connect them with topical fields of research, such as waiting-time statistics, quantum metrology, thermodynamic uncertainty relations, quantum point contacts and Maxwell's demons. + oai:arXiv.org:2303.04270v5 + quant-ph + cond-mat.stat-mech + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - Diego Forlivesi, Lorenzo Valentini, Marco Chiani + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/PRXQuantum.5.020201 + PRX Quantum 5, 020201 (2024) + Gabriel T. Landi, Michael J. Kewming, Mark T. Mitchison, Patrick P. Potts - General teleportation channel in Fermionic Quantum Theory - https://arxiv.org/abs/2312.04240 - arXiv:2312.04240v2 Announce Type: replace -Abstract: Quantum Teleportation is a very useful scheme for transferring quantum information. Given that the quantum information is encoded in a state of a system of distinguishable particles, and given that the shared bi-partite entangled state is also that of a system of distinguishable particles, the $\textit{optimal teleportation fidelity}$ of the shared state is known to be $(F_{max}d+1)/(d+1)$ with $F_{max}$ being the `maximal singlet fraction' of the shared state. However, Parity Superselection Rule (PSSR) in Fermionic Quantum Theory (FQT) puts constraint on the allowed set of physical states and operations, and thereby, leads to a different notion of Quantum entanglement - locally accessible and locally inaccessible. In the present work, we derive an expression for the $\textit{optimal teleportation fidelity}$ of locally accessible entanglement preservation, given that the quantum information to be teleported is encoded in fermionic modes of dimension $2^N \times 2^N$ using $2^N \times 2^N$-dim shared fermionic resource between the sender and receiver. To get the optimal teleportation fidelity in FQT, we introduce PSSR restricted twirling operations and establish fermionic state-channel isomorphism. Remarkably, we notice that the structure of the canonical form of twirl invariant fermionic shared state differs from that of the $\textit{isotropic state}$ -- the corresponding canonical invariant form for teleportation in Standard Quantum Theory (SQT). In this context, we also introduce restricted Clifford twirling operation that constitute the Unitary 2-design in case of FQT for experimentally validating such optimal average fidelity. Finally, we discuss the preservation of locally inaccessible entanglement for a class of fermionic teleportation channel. - oai:arXiv.org:2312.04240v2 + Unveiling the Dynamical Genesis of Quantum Entanglement in Linear Systems: Internal causality breaking in the reduced subsystem evolution + https://arxiv.org/abs/2403.09368 + arXiv:2403.09368v3 Announce Type: replace +Abstract: Utilizing the general theory of open quantum systems to investigate the exact dynamical evolution of simple bilinear systems, we discover a mechanism of the dynamical genesis of quantum entanglement. We focus in detail on the exact quantum evolution dynamics of two photonic modes (or any two bosonic modes) coupled to each other through a linear interaction, as the simplest system of open quantum systems that we have investigated in the last two decades. Such a linear coupling alone fails to produce two-mode entanglement. We also start with an initially separable pure state of the two modes. By solving exactly the quantum equation of motion without relying on the probabilistic interpretation, we find that when the initial state of one mode is different from a coherent state (a minimum uncertainty wave packet with equal variance in the conjugate quadratures that corresponds to a well-defined classically "particle"), the causality in the time-evolution of each mode is internally violated. It also leads to the emergence of quantum entanglement between the two modes. The lack of causality is the nature of statistics. We discover that it is the internal violation of causality in the reduced (subsystem) dynamical evolution that results in the emergence of entanglement and statistic probability in quantum mechanics, even though the dynamical evolution of the whole system completely obeys the deterministic Schr\"{o}dinger equation. This conclusion is valid for the quantum dynamics of more complicated composite systems. It may provide the fundamental mechanism of the dynamical genesis for both the entanglement and the statistical probability within the deterministic framework of quantum mechanics, which is the longest-standing problem that has not been fully understood since the birth of quantum mechanics. + oai:arXiv.org:2403.09368v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Sanam Khan, R. Jehadeesan, Sibasish Ghosh + 10.1063/5.0298701 + J. Chem. Phys. 163, 234107 (2025 + Shuang-Kai Yang, Wei-Min Zhang - A fixed-point algorithm for matrix projections with applications in quantum information - https://arxiv.org/abs/2312.14615 - arXiv:2312.14615v3 Announce Type: replace -Abstract: We develop a fixed-point iterative algorithm that computes the matrix projection with respect to the Bures distance on the set of positive definite matrices that are invariant under some symmetry. We prove that the fixed-point iteration algorithm converges exponentially fast to the optimal solution in the number of iterations. Moreover, it numerically shows fast convergence compared to the off-the-shelf semidefinite program solvers. Our algorithm, for the specific case of Bures-Wasserstein barycenter, recovers the fixed-point iterative algorithm originally introduced in (\'Alvarez-Esteban et al., 2016). Our proof is concise and relies solely on matrix inequalities. Finally, we discuss several applications of our algorithm in quantum resource theories and quantum Shannon theory. - oai:arXiv.org:2312.14615v3 + Warm Start of Variational Quantum Algorithms for Quadratic Unconstrained Binary Optimization Problems + https://arxiv.org/abs/2407.02569 + arXiv:2407.02569v2 Announce Type: replace +Abstract: Variational Quantum Eigensolver (VQE) is widely used in near-term hardware. However, their performances remain limited by the poor trainability and are dependent on random parameter initialization. In this work, we propose a warm start method inspired by imaginary time evolution, allowing for determining initial parameters that prioritize lower energy states in a resource-efficient way. Using classical simulations, we demonstrate that this warm start method significantly improves the success rate and reduces the number of iterations required for the convergence of VQE. The numerical results also indicate that the warm start approach effectively mitigates statistical errors arising from a finite number of measurements, and to a certain extent alleviates the effect of barren plateaus. + oai:arXiv.org:2407.02569v2 quant-ph - math-ph - math.MP - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1140/epjqt/s40507-025-00452-0 + EPJ Quantum Technology (2025) + Yahui Chai, Karl Jansen, Stefan K\"uhn, Tim Schw\"agerl, Tobias Stollenwerk + + + Operator space fragmentation in perturbed Floquet-Clifford circuits + https://arxiv.org/abs/2408.01545 + arXiv:2408.01545v3 Announce Type: replace +Abstract: Floquet quantum circuits are able to realise a wide range of non-equilibrium quantum states, exhibiting quantum chaos, topological order and localisation. In this work, we investigate the stability of operator localisation and emergence of chaos in random Floquet-Clifford circuits subjected to unitary perturbations which drive them away from the Clifford limit. We construct a nearest-neighbour Clifford circuit with a brickwork pattern and study the effect of including disordered non-Clifford gates. The perturbations are uniformly sampled from single-qubit unitaries with probability $p$ on each qubit. We show that the interacting model exhibits strong localisation of operators for $0 \le p < 1$ that is characterised by the fragmentation of operator space into disjoint sectors due to the appearance of wall configurations. Such walls give rise to emergent local integrals of motion for the circuit that we construct exactly. We analytically establish the stability of localisation against generic perturbations and calculate the average length of operator spreading tunable by $p$. Although our circuit is not separable across any bi-partition, we further show that the operator localisation leads to an entanglement bottleneck, where initially unentangled states remain weakly entangled across typical fragment boundaries. Finally, we study the spectral form factor (SFF) to characterise the chaotic properties of the operator fragments and spectral fluctuations as a probe of non-ergodicity. In the $p = 1$ model, the emergence of a fragmentation time scale is found before random matrix theory sets in after which the SFF can be approximated by that of the circular unitary ensemble. Our work provides an explicit description of quantum phases in operator dynamics and circuit ergodicity which can be realised on current NISQ devices. + oai:arXiv.org:2408.01545v3 + quant-ph + cond-mat.dis-nn + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Shrigyan Brahmachari, Roberto Rubboli, Marco Tomamichel + Marcell D. Kov\'acs, Christopher J. Turner, Lluis Masanes, Arijeet Pal - Theory of Complex Particle without Extra Dimensions - https://arxiv.org/abs/2407.03378 - arXiv:2407.03378v4 Announce Type: replace -Abstract: Complex particle is a kind of bilocal particle having unexpected symmetry, which was proposed by the authour. In the present paper, we show that critical dimension of the complex particle in Minkowski spacetime is $D = 4$, while $D = 2, 4$ or $6$ are permitted in Euclid spacetime. The origin of the restriction to the dimension is the existence of tertiary constraint in the canonical theory, quantization of which leads to an eigenvalue equation having single-valued and bounded solutions only in particular dimension of spacetime. The derivation is based on a detailed analysis of Laplace-Beltrami operator on $S^{1,D-2}$ or $S^{D-1}$. - oai:arXiv.org:2407.03378v4 + Exact spectral gaps of random one-dimensional quantum circuits + https://arxiv.org/abs/2408.11201 + arXiv:2408.11201v2 Announce Type: replace +Abstract: The spectral gap of local random quantum circuits is a fundamental property that determines how close the moments of the circuit's unitaries match those of a Haar random distribution. When studying spectral gaps, it is common to bound these quantities using tools from statistical mechanics or via quantum information-based inequalities. By focusing on the second moment of one-dimensional unitary circuits where nearest neighboring gates act on sets of qudits (with open and closed boundary conditions), we show that one can exactly compute the associated spectral gaps. Indeed, having access to their functional form allows us to prove several important results, such as the fact that the spectral gap for closed boundary condition is exactly the square of the gap for open boundaries, as well as improve on previously known bounds for approximate design convergence. Finally, we verify our theoretical results by numerically computing the spectral gap for systems of up to 70 qubits, as well as comparing them to gaps of random orthogonal and symplectic circuits. + oai:arXiv.org:2408.11201v2 + quant-ph + cs.CC + cs.IT + math.IT + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/8p5j-mxhh + Phys. Rev. A 112, 062619 (2025) + Andrew E. Deneris, Pablo Bermejo, Paolo Braccia, Lukasz Cincio, M. Cerezo + + + Continuous symmetry entails the Jordan algebra structure of finite-dimensional quantum theory + https://arxiv.org/abs/2411.19672 + arXiv:2411.19672v3 Announce Type: replace +Abstract: Symmetry postulates play a crucial role in various approaches to reconstruct quantum theory from a few basic principles. Discrete and continuous symmetries are under consideration. The continuous case better matches the physical needs for mathematical models of dynamical processes and is studied here. Applying the representation theory of the orthomodular lattices and a generalized version of Gleason's theorem for Jordan matrix algebras, we show that the continuous symmetry, together with three further requirements, entails that the underlying mathematical structure of a finite-dimensional generalized probabilistic theory becomes a simple Euclidean Jordan algebra. The further requirements are: spectrality, a strong state space and a condition called gbit property. + oai:arXiv.org:2411.19672v3 quant-ph - hep-th math-ph + math.FA math.MP - Fri, 12 Dec 2025 00:00:00 -0500 + math.OA + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - Takayuki Hori + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Gerd Niestegge - Universal adapters between quantum LDPC codes - https://arxiv.org/abs/2410.03628 - arXiv:2410.03628v4 Announce Type: replace -Abstract: We propose the repetition code adapter as a way to perform joint logical Pauli measurements within a quantum low-density parity check (LDPC) codeblock or between separate such codeblocks, thus providing a flexible tool for fault-tolerant computation with quantum LDPC codes. This adapter is universal in the sense that it works regardless of the LDPC codes involved and the logical Paulis being measured. The construction achieves joint logical Pauli measurement of $t$ weight $O(d)$ operators using $O(d)$ time and $\tilde O(td)$ additional qubits and checks, up to a factor polylogarithmic in $d$. As a special case, for some geometrically-local codes in fixed $D\ge2$ dimensions, only $O(td)$ additional qubits and checks are required instead. By extending the adapter in the case $t=2$, we also construct a toric code adapter that uses $O(d^2)$ additional qubits and checks to perform addressable logical CNOT gates on arbitrary LDPC codes via Dehn twists. To obtain these results, we develop a novel weaker form of graph edge expansion and the $\mathsf{SkipTree}$ algorithm, which ensures a sparse transformation between different weight-2 check bases for the classical repetition code. - oai:arXiv.org:2410.03628v4 + Supercorrelated decay in a quasiperiodic nonlinear waveguide: From Markovian to non-Markovian transitions + https://arxiv.org/abs/2501.03607 + arXiv:2501.03607v2 Announce Type: replace +Abstract: Mobility edges (MEs) are critical boundaries in disordered quantum systems that separate localized from extended states, significantly affecting transport properties and phase transitions. Although MEs are well-understood in single-photon systems, their manifestation in many-body contexts remains an active area of research. In this work, we investigate a one-dimensional Bose-Hubbard chain with a quasiperiodic potential modulating photon-photon interactions, effectively creating a mosaic lattice. We identify MEs for doublon states (i.e, bound photon pairs resulting from strong interactions) within the two-photon subspace. Our analytical solutions and numerical simulations confirm the existence of these MEs, extending single-photon MEs theories to the two-photon regime. Additionally, we analyze the dynamics of two emitters coupled to the waveguide, enabling the emission of supercorrelated photon pairs into the waveguide. Our findings reveal that coupling to extended states results in Markovian dynamics, characterized by exponentially supercorrelated decay, while coupling to localized states gives rise to non-Markovian dynamics, marked by suppressed decay and persistent oscillations. Here, a transition from Markovian to non-Markovian behavior occurs around the MEs of the doublons. Finally, we propose a feasible experimental implementation using superconducting circuits, providing a platform to observe the interplay between interactions and disorder in quantum systems. + oai:arXiv.org:2501.03607v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Esha Swaroop, Tomas Jochym-O'Connor, Theodore J. Yoder + http://creativecommons.org/licenses/by/4.0/ + 10.1103/4mql-32sg + Phys. Rev. A 112, 013528 (2025) + Jia-Qi Li, Tian-Yu Zhou, Xin Wang - Universal approximation of continuous functions with minimal quantum circuits - https://arxiv.org/abs/2411.19152 - arXiv:2411.19152v3 Announce Type: replace -Abstract: The conventional paradigm of quantum computing is discrete: it utilizes discrete sets of gates to realize bitstring-to-bitstring mappings, some of them arguably intractable for classical computers. In parameterized quantum approaches, the input becomes continuous and the output represents real-valued functions. While the universality of discrete quantum computers is well understood, basic questions remained open in the continuous case. We focus on universality on multivariate functions. Current approaches require either a number of qubits scaling linearly with the dimension of the input for fixed encodings, or a tunable encoding procedure in single-qubit circuits. The question of whether universality can be reached with a fixed encoding and sub-linearly many qubits remained open for the last five years. In this paper, we answer this question in the affirmative for arbitrary multivariate functions. We provide two methods: (i) a single-qubit circuit where each coordinate of the arguments to the function to represent is input independently, and (ii) a multi-qubit approach where all coordinates are input in one step, with number of qubits scaling logarithmically with the dimension of the argument of the function of interest. We view the first result of inherent and fundamental interest, whereas the second result opens the path towards representing functions whose arguments are densely encoded in a unitary operation, possibly encoding for instance quantum processes. - oai:arXiv.org:2411.19152v3 + Selective band interaction and long-range hopping in a structured environment with giant atoms + https://arxiv.org/abs/2501.07254 + arXiv:2501.07254v2 Announce Type: replace +Abstract: Giant atoms, which couple to the environment at multiple discrete points, exhibit various nontrivial phenomena in quantum optics due to their nonlocal couplings. In this study, we propose a one-dimensional cross-stitch ladder lattice featuring both a dispersive band and a flat band. By modulating the relative phase between the coupling points, the giant atom selectively interacts with either band. First, we analyze the scenario where the dispersive and flat bands intersect at two points, and the atomic frequency lies within the band. Unlike the small atom, which simultaneously interacts with both bands, a single giant atom with a controllable phase interacts exclusively with the dispersive or flat band. Second, in the bandgap regime, where two atoms interact through bound-state overlaps manifesting as dipole-dipole interactions, we demonstrate that giant atoms enable deterministic long-range hopping and energy exchange with higher fidelity compared to small atoms. These findings provide promising applications in quantum information processing, offering enhanced controllability and selectivity for quantum systems and devices. + oai:arXiv.org:2501.07254v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - 10.1103/t49h-jmty - Phys. Rev. Research 7, 043282, 2025 - Adri\'an P\'erez-Salinas, Mahtab Yaghubi Rad, Alice Barthe, Vedran Dunjko + 10.1103/PhysRevA.111.053706 + Phys. Rev. A 111, 053706 (2025) + Ying Xia, Jia-Qi Li, Xin Wang + + + Near-deterministic photon entanglement from a spin qudit in silicon using third quantisation + https://arxiv.org/abs/2502.01096 + arXiv:2502.01096v2 Announce Type: replace +Abstract: Unlike other quantum hardware, photonic quantum architectures can produce millions of qubits from a single device. However, controlling photonic qubits remains challenging, even at small scales, due to their weak interactions, making non-deterministic gates in linear optics unavoidable. Nevertheless, a single photon can readily spread over multiple modes and create entanglement within the multiple modes deterministically. Rudolph's concept of third quantization leverages this feature by evolving multiple single-photons into multiple modes, distributing them uniformly and randomly to different parties, and creating multipartite entanglement without interactions between photons or non-deterministic gates. This method requires only classical communication and deterministic entanglement within multi-mode single-photon states and enables universal quantum computing. The multipartite entanglement generated within the third quantization framework is nearly deterministic, where ``deterministic'' is achieved in the asymptotic limit of a large system size. In this work, we propose a near-term experiment using antimony donor in a silicon chip to realize third quantization. Utilizing the eight energy levels of antimony, one can generate two eight-mode single-photon states independently and distribute them to parties. This enables a random multipartite Bell-state experiment, achieving a Bell state with an upper-bound efficiency of 87.5% among 56 random pairs without non-deterministic entangling gates. This approach opens alternative pathways for silicon-based photonic quantum computing. + oai:arXiv.org:2502.01096v2 + quant-ph + cond-mat.mes-hall + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + G\"ozde \"Ust\"un, Samuel Elman, Jarryd J. Pla, Andrew C. Doherty, Andrea Morello, Simon J. Devitt - An Adaptive Mixer Allocation Algorithm for the Quantum Alternating Operator Ansatz - https://arxiv.org/abs/2412.19621 - arXiv:2412.19621v2 Announce Type: replace -Abstract: Recently, Hadfield et al. proposed the quantum alternating operator ansatz algorithm (QAOA+), an extension of the quantum approximate optimization algorithm (QAOA), to solve constrained combinatorial optimization problems (CCOPs). Compared with QAOA, QAOA+ enables the search for optimal solutions within a feasible solution space by encoding problem constraints into the mixer Hamiltonian, thereby reducing the search space and eliminating the possibility of yielding infeasible solutions. However, QAOA+ may incur high overall gate costs when the mixer is applied to all qubits in each layer, and each mixer is costly to implement. To address this challenge, an adaptive mixer allocation strategy is tailored for QAOA+. The resulting algorithm, which integrates this strategy into the original QAOA+ framework, is referred to as AMA-QAOA+. Unlike QAOA+, AMA-QAOA+ adaptively applies the mixer to a subset of qubits in each layer of the mixer unitary operator based on an evaluation function. The performance of AMA-QAOA+ is evaluated on the maximum independent set problem. Numerical simulation results show that, under the same number of optimization runs, AMA-QAOA+ achieves better solution quality than QAOA+, with the optimal approximation ratio improved by $5.30\%$ on ER random graphs and $5.41\%$ on 3-regular graphs. Moreover, AMA-QAOA+ significantly reduces the CNOT gate consumption, requiring only $15.30\%$ and $25.18\%$ of the CNOT gates used by QAOA+ on ER and 3-regular random graphs, respectively. These results demonstrate that AMA-QAOA+ enhances solution quality and computational efficiency, enabling the design of more compact and resource-efficient quantum circuits. - oai:arXiv.org:2412.19621v2 + Weak continuous measurements require more work than strong ones + https://arxiv.org/abs/2502.09732 + arXiv:2502.09732v3 Announce Type: replace +Abstract: Understanding the energy cost of quantum measurement process and its connection to the measurement performance faces the challenge of modeling the objectification process. The latter, turns the measurement result into an objective fact, available to independent observers, and is responsible for the measurement irreversibility. To address this issue, we propose and analyze a dynamical model of quantum measurement, able to capture nonideal (weak and inefficient) measurements. In this model, the objectification is induced by a contact with a macroscopic reservoir at equilibrium which is responsible for the redundant broadcast of the measurement outcome (producing a Spectrum Broadcast Structure (SBS) state) while inducing decoherence in the pointer basis, in the line of the theory of quantum Darwinism. We analyze the performance of the obtained measurement process by introducing figures of merit to quantify the strength of the measurement and its efficiency. We also derive and a lower bound on the measurement work cost that we can relate to the measurement quality. We take as an illustration the readout of a qubit via its coupling to a harmonic oscillator. We investigate the long sequences of extremely short and weak measurements (a.k.a continuous measurements), to find under which conditions they converge to an ideal (projective) measurement and analyze their work cost. Surprisingly, we find that a sequence converging to projective measurement has a much larger work cost than an equivalent strong measurement obtained from a single intense interaction with the apparatus. We extend this result to a large class of models owing to scaling arguments. Our analysis offers new insights into the trade-offs between measurement strength, energy consumption, and information extraction in quantum measurement protocols. + oai:arXiv.org:2502.09732v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiao-Hui Ni, Yu-Sen Wu, Bin-Bin Cai, Wen-Min Li, Su-Juan Qin, Fei Gao + Lorena Ballesteros Ferraz, Cyril Elouard - Recurrence Criteria for Reducible Homogeneous Open Quantum Walks on the Line - https://arxiv.org/abs/2501.01249 - arXiv:2501.01249v3 Announce Type: replace -Abstract: In this paper, we study the recurrence of Open Quantum Walks induced by finite-dimensional coins on the line ($\mathbb{Z}$) and on the grid ($\mathbb{Z}^2$). Two versions are considered: discrete-time open quantum walks (OQW) and continuous-time open quantum walks (CTOQW). We present three distinct recurrence criteria for OQWs on $\mathbb{Z}$, each adapted to different types of coins. The first criterion applies to coins whose auxiliary map has a unique invariant state, resulting in the first recurrence criterion for Lazy OQWs. The second one applies to Lazy OQWs of dimension 2, where we provide a complete characterization of the recurrence for this low-dimensional case. The third one presents a general criterion for finite-dimensional coins in the non-lazy case, which generalizes many of the previously known results for OQWs on $\mathbb{Z}$. Also, we present a general recurrence criterion for OQWs on $\mathbb{Z}^2$ via the open quantum jump chain, obtained from a recurrence criterion for CTOQWs on $\mathbb{Z}^2$. - oai:arXiv.org:2501.01249v3 + Measurement-device-independent Schmidt number certification of all entangled states + https://arxiv.org/abs/2502.13296 + arXiv:2502.13296v3 Announce Type: replace +Abstract: Bipartite quantum states with higher Schmidt numbers have been shown to outperform those with lower Schmidt numbers in various quantum information processing tasks, highlighting the operational advantage of entanglement dimensionality. Certifying the Schmidt number of such states is therefore crucial for efficient resource utilisation. Ideally, this certification should rely as little as possible on the certifying devices to ensure robustness against their potential imperfections. Fully device-independent certification via Bell-nonlocal games offers strong robustness but suffers from fundamental limitations: it cannot certify the Schmidt number of all entangled states. We demonstrate that this insufficiency of Bell-nonlocal games is not limited to entangled states that do not exhibit Bell-nonlocality. Specifically, we prove the existence of Bell-nonlocal states whose Schmidt number cannot be certified by any Bell-nonlocal game when the parties are restricted to local projective measurements. To overcome this, we develop a measurement-device-independent certification method based on semiquantum nonlocal games, which assume trusted preparation devices but treat measurement devices as black boxes. We prove that for any bipartite state with Schmidt number exceeding $r$, there exists a semiquantum nonlocal game that can certify its Schmidt number. Finally, we provide an explicit construction of such a semiquantum nonlocal game based on an optimal Schmidt number witness operator. + oai:arXiv.org:2502.13296v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Newton Loebens + http://creativecommons.org/licenses/by/4.0/ + 10.1103/nlz1-h6qr + Phys. Rev. A 112, 062434 (2025) + Saheli Mukherjee, Bivas Mallick, Arun Kumar Das, Amit Kundu, Pratik Ghosal - Tight relations and equivalences between smooth relative entropies - https://arxiv.org/abs/2501.12447 - arXiv:2501.12447v4 Announce Type: replace -Abstract: The precise one-shot characterisation of operational tasks in classical and quantum information theory relies on different forms of smooth entropic quantities. A particularly important connection is between the hypothesis testing relative entropy and the smoothed max-relative entropy, which together govern many operational settings. We first strengthen this connection into a type of equivalence: we show that the hypothesis testing relative entropy is equivalent to a variant of the smooth max-relative entropy based on the information spectrum divergence, which can be alternatively understood as a measured smooth max-relative entropy. Furthermore, we improve a fundamental lemma due to Datta and Renner that connects the different variants of the smoothed max-relative entropy, introducing a modified proof technique based on matrix geometric means and a tightened gentle measurement lemma. We use the unveiled connections and tools to strictly improve on previously known one-shot bounds and duality relations between the smooth max-relative entropy and the hypothesis testing relative entropy, establishing provably tight bounds between them. We use these results to refine other divergence inequalities, in particular sharpening bounds that connect the max-relative entropy with R\'enyi divergences. - oai:arXiv.org:2501.12447v4 + Practical Unclonable Encryption with Continuous Variables + https://arxiv.org/abs/2503.02648 + arXiv:2503.02648v2 Announce Type: replace +Abstract: We propose the first continuous-variable (CV) unclonable encryption scheme, extending the paradigm of quantum encryption of classical messages (QECM) to CV systems. In our construction, a classical message is first encrypted classically and then encoded using an errorcorrecting code. Each bit of the codeword is mapped to a CV mode by creating a coherent state which is squeezed in the q or p quadrature direction, with a small displacement that encodes the bit. The squeezing directions are part of the encryption key. We prove unclonability in the framework introduced by Broadbent and Lord, via a reduction of the cloning game to a CV monogamy-of-entanglement game. Furthermore, we demonstrate that our scheme can be readily implemented with current technology. By incorporating realistic imperfections such as channel noise and detector inefficiencies, we show that the protocol remains robust under these conditions. + oai:arXiv.org:2503.02648v2 quant-ph - cs.IT - math-ph - math.IT - math.MP - Fri, 12 Dec 2025 00:00:00 -0500 + cs.CR + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Bartosz Regula, Ludovico Lami, Nilanjana Datta + http://creativecommons.org/licenses/by/4.0/ + Arpan Akash Ray, Boris \v{S}kori\'c - Nonstabilizerness dynamics in many-body localized systems - https://arxiv.org/abs/2503.07468 - arXiv:2503.07468v3 Announce Type: replace -Abstract: Nonstabilizerness, also known as ``magic'', quantifies the deviation of quantum states from stabilizer states, capturing the complexity necessary for quantum computational advantage. In this study, we investigate the dynamics of nonstabilizerness in disordered many-body localized (MBL) systems using the stabilizer R\'enyi entropy (SRE). Leveraging a phenomenological description based on the $\ell$-bit model, we analytically and numerically demonstrate that interactions profoundly influence nonstabilizerness spreading, inducing a power-law growth of SRE that markedly contrasts with the rapid saturation observed in ergodic systems. We validate our theoretical predictions through numerical simulations of the disordered transverse-field Ising model, showing excellent agreement across various disorder strengths, system sizes, and initial states. Additionally, we uncover a universal relationship between SRE and entanglement entropy, revealing their common scaling in the MBL regime independent of disorder strength and system size. Our results offer critical insights into the interplay of disorder, interactions, and complexity in quantum many-body systems. - oai:arXiv.org:2503.07468v3 + On physicality of electromagnetic potential from causal structure of flux quantization + https://arxiv.org/abs/2503.15410 + arXiv:2503.15410v2 Announce Type: replace +Abstract: Recent work by Vaidman [Phys. Rev. A 86,040101 (2012)] showed that Aharonov-Bohm effect can be explained in terms of local fields, thus effectively restating an old problem of physicality of potentials. In this work, we propose an argument demonstrating the physicality of electromagnetic potential (upon the assumption of locality) based on the causal structure in flux quantization setup. Crucially, we discuss the fundamental difference between the considered setup and the Aharonov-Bohm experiment that allows for avoiding Vaidman's loophole in our scenario. + oai:arXiv.org:2503.15410v2 quant-ph - cond-mat.dis-nn - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - 10.1103/xfp5-hhs4 - Phys. Rev. Lett. 135, 240404 (2025) - Pedro R. Nic\'acio Falc\~ao, Piotr Sierant, Jakub Zakrzewski, Emanuele Tirrito + Konrad Schlichtholz, Marcin Markiewicz - Approximation Methods for Simulation and Equivalence Checking of Noisy Quantum Circuits - https://arxiv.org/abs/2503.10340 - arXiv:2503.10340v2 Announce Type: replace -Abstract: In the current NISQ (Noisy Intermediate-Scale Quantum) era, simulating and verifying noisy quantum circuits is crucial but faces challenges such as quantum state explosion and complex noise representations, constraining simulation and equivalence checking to circuits with a limited number of qubits. This paper introduces an approximation algorithm for simulating and assessing the equivalence of noisy quantum circuits, specifically designed to improve scalability under low-noise conditions. The approach utilizes a novel tensor network diagram combined with singular value decomposition to approximate the tensors of quantum noises. The implementation is based on Google's TensorNetwork Python package for contraction. Experimental results on realistic quantum circuits with realistic hardware noise models indicate that our algorithm can simulate and check the equivalence of QAOA (Quantum Approximate Optimization Algorithm) circuits with around 200 qubits and 20 noise operators, outperforming state-of-the-art approaches in scalability and speed. - oai:arXiv.org:2503.10340v2 + Enhanced Variational Quantum Kolmogorov-Arnold Network + https://arxiv.org/abs/2503.22604 + arXiv:2503.22604v3 Announce Type: replace +Abstract: The Kolmogorov-Arnold Network (KAN) is a novel multi-layer network model recognized for its efficiency in neuromorphic computing, where synapses between neurons are trained linearly. Computations in KAN are performed by generating a polynomial vector from the state vector and layer-wise trained synapses, enabling efficient processing. While KAN can be implemented on quantum computers using block encoding and Quantum Signal Processing, these methods require fault-tolerant quantum devices, making them impractical for current Noisy Intermediate-Scale Quantum (NISQ) hardware. We propose the Enhanced Variational Quantum Kolmogorov-Arnold Network (EVQKAN) to overcome this limitation, which emulates KAN through variational quantum algorithms. The EVQKAN ansatz employs a tiling technique to emulate layer matrices, leading to significantly higher accuracy compared to conventional Variational Quantum Kolmogorov-Arnold Network (VQKAN) and Quantum Neural Networks (QNN), even with a smaller number of layers. EVQKAN achieves superior performance with a single-layer architecture, whereas QNN and VQKAN typically struggle. Additionally, EVQKAN eliminates the need for Quantum Signal Processing, enhancing its robustness to noise and making it well-suited for practical deployment on NISQ-era quantum devices. + oai:arXiv.org:2503.22604v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.comp-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Mingyu Huang, Ji Guan, Wang Fang, Mingsheng Ying + Hikaru Wakaura, Rahmat Mulyawan, Andriyan B. Suksmono - Computing band gaps of periodic materials via sample-based quantum diagonalization - https://arxiv.org/abs/2503.10901 - arXiv:2503.10901v2 Announce Type: replace -Abstract: A key objective of computational solid state physics is to predict electronic properties of periodic materials. However, electronic structure simulations based on density functional theory fail to predict experimental results if correlations are not properly accounted for. Here, we report a sample-based quantum diagonalization workflow for simulating electronic states of periodic materials, and for predicting their band gaps. To that end, we devise a general lattice Hamiltonian representation in which material-specific, electronic interaction parameters are obtained self-consistently. Two exemplar, wide-gap materials - hafnium dioxide and zirconium dioxide - are expressed as quantum circuits that leverage the lattice representation with a materials-specific parametrization. We sample the quantum circuits on a state-of-the-art, superconducting quantum processor and diagonalize the lattice Hamiltonian in the reduced configuration subspaces with standard techniques. Our method outperforms select quantum-chemical benchmarks as well as approaches based on density functional theory, the standard reference in materials simulation of solids. Importantly, the quantum-computed band gap predictions for the two dielectrics agree with independent lab experiments. In essence, quantum-classical hybrid simulation workflows on pre-fault tolerant quantum computers produce useful, experimentally verifiable property predictions in applied materials science. - oai:arXiv.org:2503.10901v2 + Double-bracket algorithm for quantum signal processing without post-selection + https://arxiv.org/abs/2504.01077 + arXiv:2504.01077v3 Announce Type: replace +Abstract: Quantum signal processing (QSP), a framework for implementing matrix-valued polynomials, is a fundamental primitive in various quantum algorithms. Despite its versatility, a potentially underappreciated challenge is that all systematic protocols for implementing QSP rely on post-selection. This can impose prohibitive costs for tasks when amplitude amplification cannot sufficiently improve the success probability. For example, in the context of ground-state preparation, this occurs when using a too poor initial state. In this work, we introduce a new formula for implementing QSP transformations of Hermitian matrices, which requires neither auxiliary qubits nor post-selection. Rather, using approximation to the exact unitary synthesis, we leverage the theory of the double-bracket quantum algorithms to provide a new quantum algorithm for QSP, termed Double-Bracket QSP (DB-QSP). The algorithm requires the energy and energetic variance of the state to be measured at each step and has a recursive structure, which leads to circuit depths that can grow super exponentially with the degree of the polynomial. With these strengths and caveats in mind, DB-QSP should be viewed as complementing the established QSP toolkit. In particular, DB-QSP can deterministically implement low-degree polynomials to "warm start" QSP methods involving post-selection. + oai:arXiv.org:2504.01077v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Alan Duriez, Pamela C. Carvalho, Marco Antonio Barroca, Federico Zipoli, Ben Jaderberg, Rodrigo Neumann Barros Ferreira, Kunal Sharma, Antonio Mezzacapo, Benjamin Wunsch, Mathias Steiner + Yudai Suzuki, Bi Hong Tiang, Jeongrak Son, Nelly H. Y. Ng, Zo\"e Holmes, Marek Gluza - A note on the quantum Wielandt inequality - https://arxiv.org/abs/2504.21638 - arXiv:2504.21638v3 Announce Type: replace -Abstract: In this note, we prove that the index of primitivity of any primitive unital Schwarz map is at most $2(D-1)^2$, where $D$ is the dimension of the underlying matrix algebra. This inequality was first proved by Rahaman for Schwarz maps which were both unital and trace preserving. As we show, the assumption of unitality is basically innocuous, but in general not all primitive unital Schwarz maps are trace preserving. Therefore, the precise purpose of this note is to showcase how to apply the method of Rahaman to unital primitive Schwarz maps that don't preserve trace. As a corollary of this theorem, we show that the index of primitivity of any primitive 2-positive map is at most $2(D-1)^2$, so in particular this bound holds for arbitrary primitive completely positive maps. We briefly discuss of how this relates to a conjecture of Perez-Garcia, Verstraete, Wolf and Cirac. - oai:arXiv.org:2504.21638v3 + Scalable low-latency entanglement distribution for distributed quantum computing + https://arxiv.org/abs/2504.05567 + arXiv:2504.05567v3 Announce Type: replace +Abstract: Practical distributed quantum computing and error correction require quantum networks with high-qubit-rate, high-fidelity, and low-reconfiguration-latency. Unfortunately, current approaches are limited by fundamental constraints: single-channel entanglement rates remain at the MHz level with millisecond-level reconfiguration, which is insufficient for fault-tolerant distributed quantum computing. Here, we propose a quantum network architecture that leverages reconfigurable quantum interfaces and wavelength-selective switches to overcome bandwidth and latency constraints. By tuning the frequency and temporal modes of photonic qubits across dense wavelength division multiplexing (DWDM) channels, our protocol achieves an entanglement generation rate of up to 183.4 MHz based on our comprehensive modeling of the networked cold atom computing systems. Our architecture enables nanosecond-scale network reconfiguration with low loss, low infidelity, and high dimensionality. Our modeling and simulation are designed for deployable distributed quantum computing and error correction, integrating the quantum interface, network switching, circuit compilation, and execution into a unified framework. The proposed architecture is fully compatible with industry-standard DWDM infrastructure, providing a scalable and cost-effective foundation for distributed quantum computing. + oai:arXiv.org:2504.05567v3 quant-ph - cs.IT - math.IT - math.OA - Fri, 12 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Owen Ekblad + 10.1364/OPTICAQ.569352 + Optica Quantum Vol. 3, Issue 6, pp. 606-616 (2025) + Jiapeng Zhao, Yang Xu, Xiyuan Lu, Eneet Kaur, Michael Kilzer, Ramana Kompella, Robert W. Boyd, Reza Nejabati - Noisy simulations of Quantum Walk and Quantum Walk search via Quantum Cellular Automata on a semiconducting spin processor emulator - https://arxiv.org/abs/2505.14134 - arXiv:2505.14134v2 Announce Type: replace -Abstract: In this work we map NISQ-friendly implementations of the non-interacting QCA to a circuit Quantum Electrodynamics (cQED) hardware. We perform both noiseless and noisy simulations of the QCA one particle sector, namely the Quantum Walk, on $N$-cycles and $N \times N$ torus graphs. Moreover, within this framework, we also investigate the search problem and present a circuit for preparing the W state (i.e., the Dicke state with hamming weight one) using only N-1 $\sqrt{\text{iSWAP}}$ gates and no ancilla qubits. The noiseless simulations are conducted with the Qiskit Aer simulator, while the noisy simulations with C12 Quantum Electronics' in-house noisy emulator, \textit{Callisto}. We benchmark the performance of our implementations by analyzing the simulations via relevant metrics and quantities such as the state count distributions, the Hellinger Fidelity, the $\ell^{1}$ distance, the hitting time, and success probability. Our results demonstrate that the QCA framework, in combination with cQED processors, holds promise as an effective platform for early NISQ implementations of Quantum Walk and Quantum Walk Search algorithms. - oai:arXiv.org:2505.14134v2 + End-to-End Portfolio Optimization with Quantum Annealing + https://arxiv.org/abs/2504.08843 + arXiv:2504.08843v2 Announce Type: replace +Abstract: Hybrid-quantum classical optimization has emerged as a promising direction for addressing financial decision problems under current quantum hardware constraints. In this work we present a practical end-to-end portfolio optimization pipeline that combines (i) a continuous mean-variance and Sharpe-ratio formulation, (ii) a QUBO/CQM-based discrete asset selection stage solved using D-Wave's hybrid quantum annealing solver, (iii) classical convex optimization for computing optimal asset weights, and (iv) a quarterly rebalancing mechanism. Rather than claiming quantum advantage, our goal is to evaluate the feasibility and integration of these components within a deployable financial workflow. We empirically compare our hybrid pipeline against a fund manager in real time and indexes used in Indian stock market. The results indicate that the proposed framework can construct diversified portfolios and achieve competitive returns. We also report computational considerations and scalability observations drawn from the hybrid solver behaviour. While the experiments are limited to moderate sized portfolios dictated by current annealing hardware and QUBO embedding constraints, the study illustrates how quantum assisted selection and classical allocation can be combined coherently in a real-world setting. This work emphasizes methodological reproducibility and practical applicability, and aims to serve as a step toward larger-scale financial optimization workflows as quantum annealers continue to mature. + oai:arXiv.org:2504.08843v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + econ.GN + math.OC + q-fin.EC + q-fin.PM + q-fin.RM + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Andrea Mammola, Quentin Schaeverbeke, Giuseppe Di Molfetta + Sai Nandan Morapakula, Sangram Deshpande, Rakesh Yata, Rushikesh Ubale, Uday Wad, Kazuki Ikeda - Quantum Imaginary-Time Evolution with Polynomial Resources in Time - https://arxiv.org/abs/2507.00908 - arXiv:2507.00908v3 Announce Type: replace -Abstract: Imaginary-time evolution is fundamental for analyzing quantum many-body systems, yet classical simulation requires exponentially growing resources in both system size and evolution time. While quantum approaches reduce the system-size scaling, existing methods rely on heuristic techniques with measurement precision or success probability that deteriorates as evolution time increases. We present a quantum algorithm that prepares normalized imaginary-time evolved states using an adaptive normalization factor to maintain a stable success probability over long imaginary-time intervals. Our algorithm approximates the target state with error polynomially small in the inverse imaginary time using a polynomial number of elementary quantum gates and a single ancilla qubit, with success probability close to one. When the initial state has reasonable overlap with the ground state, this algorithm also achieves polynomial resource cost in the system size. Numerical experiments validate our theoretical analysis for evolution time up to 50, demonstrating the algorithm's effectiveness for long-time evolution. Building on this technique, we further develop imaginary-time-evolution-based algorithms for ground-state-related problems and for simulating open quantum systems. These algorithms reduce circuit depth compared with existing methods and illustrate the effectiveness of imaginary-time evolution in early fault-tolerant quantum computing. - oai:arXiv.org:2507.00908v3 + A Relativistic Pseudo-Unitary Version of Schwinger's Quantum Mechanical Symbolism of Atomic Measurements and a Prospect for a New Relativistic Quantum Information Theory + https://arxiv.org/abs/2505.06559 + arXiv:2505.06559v3 Announce Type: replace +Abstract: The measurement processes that are traditionally described within the realm of non-relativistic quantum mechanics are transcribed into the covariant framework of Cartan's space, the four-valued representation space of the restricted conformal group for special relativity. It is assumed at the outset that the non-relativistic quantum measurement mechanisms of state reductions as well as the definition of Born probabilities should remain unaltered when the passage to the covariant framework is worked out. The correlations between observations registered in different spacetime frames, concerning intermediate steps and outcomes of microscopic measurements, are attained through the implementation of the orthochronous proper Poincar\'e subgroup of an appropriate realization of SU(2,2). It appears that the overall work may supply an elementary theoretical background to the construction of relativistic quantum computational gates whilst suggesting that the non-locality feature of the old quantum mechanics should be reconsidered within a relativistic formulation. The important question as to whether quantum computational processes should bear an invariant character is then raised. + oai:arXiv.org:2505.06559v3 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + J. G. Cardoso + + + Heisenberg limit in phase measurements: the threshold detection approach + https://arxiv.org/abs/2505.06714 + arXiv:2505.06714v2 Announce Type: replace +Abstract: We analyze the fundamental limits of phase measurement precision, provided by the standard (single- and two-arm) optical interferometers using the Gaussian (squeezed coherent) quantum states of the probing light. We consider two types of the measurements of the output light -- the homodyne measurement and the non-linear threshold measurement that provides the sensitivity saturating the quantum Cramer-Rao bound. + For all considered cases, we calculate the best sensitivity $\Delta\phi_0$ achievable at some given value of phase and the range $\delta\phi$ around this value within which the sensitivity is close to $\Delta\phi_0$. We show that in all cases, the Heisenberg scaling $\Delta\phi = K/N$ can be reached, where $K\sim1$ is a numerical prefactor and $N$ is the mean photon number. We show also that $\delta\phi$ strongly depends on $K$. + oai:arXiv.org:2505.06714v2 + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + D. I. Salykina, V. S. Liamin, V. L. Gorshenin, B. N. Nougmanov, F. Ya. Khalili + + + Detecting genuine multipartite entanglement using moments of positive maps + https://arxiv.org/abs/2506.00162 + arXiv:2506.00162v2 Announce Type: replace +Abstract: Genuine multipartite entanglement (GME) represents the strongest form of entanglement in multipartite systems, providing significant advantages in various quantum information processing tasks. In this work, we propose an experimentally feasible scheme for detecting GME, based on the truncated moments of positive maps. Our method avoids the need for full state tomography, making it scalable for larger systems. We provide illustrative examples of both pure and mixed states to demonstrate the efficacy of our formalism in detecting inequivalent classes of tripartite genuine entanglement. We further demonstrate the detection of quadripartite genuine entanglement, underscoring the effectiveness of our method in identifying entanglement beyond the tripartite case. Finally, we present a proposal for realising these moments in real experiments. + oai:arXiv.org:2506.00162v2 + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Lei Zhang, Jizhe Lai, Xian Wu, Xin Wang + 10.1103/ffch-xyv2 + Phys. Rev. A 112, 062428 (2025) + Saheli Mukherjee, Bivas Mallick, Sahil Gopalkrishna Naik, Ananda G. Maity, A. S. Majumdar - Efficient Gate Reordering for Distributed Quantum Compiling in Data Centers - https://arxiv.org/abs/2507.01090 - arXiv:2507.01090v2 Announce Type: replace -Abstract: Just as classical computing relies on distributed systems, the quantum computing era requires new kinds of infrastructure and software tools. Quantum networks will become the backbone of hybrid, quantum-augmented data centers, in which quantum algorithms are distributed over a local network of quantum processing units (QPUs) interconnected via shared entanglement. In this context, it is crucial to develop methods and software that minimize the number of inter-QPU communications. Here we describe key features of the quantum compiler araQne, which is designed to minimize distribution cost, measured by the number of entangled pairs required to distribute a monolithic quantum circuit using gate teleportation protocols. We establish the crucial role played by circuit reordering strategies, which strongly reduce the distribution cost compared to a baseline approach. - oai:arXiv.org:2507.01090v2 + Quantum Data Centers: Why Entanglement Changes Everything + https://arxiv.org/abs/2506.02920 + arXiv:2506.02920v2 Announce Type: replace +Abstract: The Quantum Internet is key for distributed quantum computing, by interconnecting multiple quantum processors into a virtual quantum computation system. This allows to scale the number of qubits, by overcoming the inherent limitations of noisy-intermediate-scale quantum (NISQ) devices. Thus, the Quantum Internet is the foundation for large-scale, fault-tolerant quantum computation. Among the distributed architectures, Quantum Data Centers emerge as the most viable in the medium-term, since they integrate multiple quantum processors within a localized network infrastructure, by allowing modular design of quantum networking. We analyze the physical and topological constraints of Quantum Data Centers, by emphasizing the role of entanglement orchestrators in dynamically reconfiguring network topologies through local operations. We examine the major hardware challenge of quantum transduction, essential for interfacing heterogeneous quantum systems. Furthermore, we explore how interconnecting multiple Quantum Data Centers could enable large-scale quantum networks. We discuss the topological constraints of such a scaling and identify open challenges, including entanglement routing and synchronization. The carried analysis positions Quantum Data Centers as both a practical implementation platform and strategic framework for the future Quantum Internet. + oai:arXiv.org:2506.02920v2 quant-ph - cs.DC - Fri, 12 Dec 2025 00:00:00 -0500 + cs.NI + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1098/rsta.2024.0518 + Angela Sara Cacciapuoti, Claudio Pellitteri, Jessica Illiano, Laura d'Avossa, Francesco Mazza, Siyi Chen, Marcello Caleffi + + + End-to-End Efficient Quantum Thermal and Ground State Preparation Made Simple + https://arxiv.org/abs/2508.05703 + arXiv:2508.05703v2 Announce Type: replace +Abstract: We propose new quantum algorithms for thermal and ground state preparation based on system-bath interactions. These algorithms require only forward evolution under a system-bath Hamiltonian in which the bath is a single reusable ancilla qubit, making them especially well-suited for early fault-tolerant quantum devices. By carefully designing the bath and interaction Hamiltonians, we prove that the fixed point of the dynamics accurately approximates the desired quantum state. Furthermore, we establish theoretical guarantees on the mixing time, and thereby providing a rigorous justification for the end-to-end efficiency of system-bath interaction models in thermal and ground state preparation, for several physically relevant systems. + oai:arXiv.org:2508.05703v2 + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Zhiyan Ding, Yongtao Zhan, John Preskill, Lin Lin + + + Expressivity Limits in Quantum Walk-based Optimization + https://arxiv.org/abs/2508.05749 + arXiv:2508.05749v3 Announce Type: replace +Abstract: Quantum algorithms have emerged as a promising tool to solve combinatorial optimization problems. The quantum walk optimization algorithm (QWOA) is one such variational approach that has recently gained attention. In the broader context of variational quantum algorithms (VQAs), understanding the expressivity of the ansatz has proven critical for evaluating their performance. A key method to study this aspect involves analyzing the dimension of the dynamic Lie algebra (DLA). In this work, we derive novel upper bounds on the DLA dimension for QWOA applied to arbitrary optimization problems. Specifically, we show that the DLA dimension scales at most quadratically with the number of distinct eigenvalues of the problem Hamiltonian. As a consequence, our bound guarantees a polynomial DLA dimension with respect to the input size for optimization problems in the class $\mathsf{NPO}\text{-}\mathsf{PB}$. This result, coupled with recently established performance bounds for QWOA, allows us to identify complexity-theoretic conditions under which QWOA must be overparameterized to obtain optimal or approximate solutions for $\mathsf{NPO}\text{-}\mathsf{PB}$ problems. + oai:arXiv.org:2508.05749v3 + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Riccardo Mengoni, Walter Nadalin, Mathys Rennela, Jimmy Rotureau, Tom Darras, Julien Laurat, Eleni Diamanti, Ioannis Lavdas + Guilherme A. Bridi, Debbie Lim, Lirand\"e Pira, Raqueline A. M. Santos, Franklin de L. Marquezino, Soumik Adhikary - Local-Frame Covariance and the Relational Origin of Quantum Causal Order - https://arxiv.org/abs/2508.17075 - arXiv:2508.17075v4 Announce Type: replace -Abstract: The process-matrix framework models quantum correlations without assuming a predefined global causal order, yet its standard Choi-Jamiolkowski construction implicitly presupposes a globally aligned Hilbert-space basis across all local laboratories. This makes the formalism causally indefinite yet kinematically absolute. To achieve full relational consistency, we impose the principle of local frame independence: physical predictions must remain invariant under independent unitary redefinitions of each laboratory's local basis. We formalize this requirement as a local gauge symmetry and derive the corresponding covariant representation of any process by averaging over the symmetry group. The image of this twirling operation forms a strict subset of the cone of causally separable processes. Covariance thus enforces a superselection rule for causal order, showing that indefinite causal order is not an intrinsic feature of nature but a relational coherence that exists only relative to a physical system establishing a shared quantum reference frame. - oai:arXiv.org:2508.17075v4 + Unified quantification of entanglement and magic in information scrambling and their trade-off relation + https://arxiv.org/abs/2508.11969 + arXiv:2508.11969v2 Announce Type: replace +Abstract: Entanglement and magic are among the most fundamental properties unique to quantum systems. Each quantity captures a different aspect of non-classical behavior, and each can be regarded as a resource within its own operational setting. However, the interrelation between them has not yet been fully clarified, and whether a more fundamental measure exists remains an open question. Addressing these issues is essential for deepening our understanding of quantumness. In this study, we establish a unified resource theory of information scrambling, consisting of two types: entanglement scrambling and magic scrambling. We introduce a measure that jointly characterizes both types of scrambling. This unified approach reveals a rigorous trade-off relation between entanglement and magic scrambling, as the exact maximum value of the proposed measure can be derived analytically. Furthermore, we quantify the scrambling capability of unitary transformations in terms of their ability to amplify this measure. Our work provides insights into the connection between entanglement and magic that extend beyond the context of information scrambling. + oai:arXiv.org:2508.11969v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Mao Kaneyasu, Yoshihiko Hasegawa + + + Quantum Fisher information as a witness of non-Markovianity and criticality in the spin-boson model + https://arxiv.org/abs/2508.16413 + arXiv:2508.16413v3 Announce Type: replace +Abstract: The quantum Fisher information, the quantum analogue of the classical Fisher information, is a central quantity in quantum metrology and quantum sensing due to its connection to parameter estimation and fidelity susceptibility. Using numerically exact methods applied to a paradigmatic open quantum system, the spin-boson model, we calculate both static and dynamical quantum Fisher information matrix elements with respect to spin-bath couplings and magnetic field strengths. As the spin-bath interaction increases, we first show that the coupling-coupling matrix elements relative to the ground state of the Hamiltonian are linked to the entanglement growth and signal the Berezinskii-Kosterlitz-Thouless quantum phase transition through their non-monotonic behavior. We also point out that the static quantum Fisher information exhibits a non-perturbative behavior in the zero-coupling limit, which we justify with an analytic argument. Furthermore, we demonstrate that the time-dependent matrix elements can reveal non-Markovian effects as well as the transition from the coherent to incoherent regime at the Toulouse point, remaining robust under pure dephasing noise. Non-monotonic signatures of the quantum Fisher information matrix reflect changes in quantum resources such as entanglement and coherence, quantify non-Markovian behavior, and enable criticality-enhanced quantum sensing, thereby shedding light on key features of open quantum systems. + oai:arXiv.org:2508.16413v3 + quant-ph + cond-mat.stat-mech + physics.comp-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Issam Ibnouhsein + 10.1103/fq4l-8v5g + Phys. Rev. B 112, 224314 (2025) + Daniele Parlato, Grazia Di Bello, Fabrizio Pavan, Giulio De Filippis, Carmine Antonio Perroni - Achieving quantum-limited sub-Rayleigh identification of incoherent sources with arbitrary intensities - https://arxiv.org/abs/2509.03511 - arXiv:2509.03511v2 Announce Type: replace -Abstract: The Rayleigh diffraction limit imposes a fundamental restriction on the resolution of direct imaging systems, hindering the identification of incoherent optical sources, such as celestial bodies in astronomy and fluorophores in bioimaging. Recent advances in quantum sensing have shown that this limit can be circumvented through spatial demultiplexing (SPADE) and photon detection, i.e. a semi-classical detection strategy. However, the general optimality for arbitrary intensity distributions and bright sources remains unproven. In this work, we develop a general model for incoherent light with arbitrary intensity undergoing diffraction. We employ this framework to compute the quantum Chernoff exponent for generic incoherent-source discrimination problems, focusing on the sub-diffraction regime. We show that, surprisingly, SPADE measurements saturate the quantum Chernoff bound only when certain compatibility conditions are met. These findings suggest that collective measurements may actually be needed to achieve the ultimate quantum Chernoff bound for the discrimination of specific incoherent sources. For the fully general case, our analysis can still be used to find the best SPADE configurations, generally achieved through a rotation of the SPADE interferometer that depends on the discrimination task. We also simulated the efficiency of a simplified Bayesian test that we developed for this identification task and show that the saturation of the Chernoff bound is already achieved for a finite number of repetitions $N\leqslant 5000$. Our results advance the theory of quantum-limited optical discrimination, with possible applications in diagnostics, automated image interpretation, and galaxy identification. - oai:arXiv.org:2509.03511v2 + Direct probing of the simulation complexity of open quantum many-body dynamics + https://arxiv.org/abs/2508.19959 + arXiv:2508.19959v2 Announce Type: replace +Abstract: Simulating open quantum systems is key to understanding non-equilibrium processes, as persistent influence from the environment induces dissipation and can give rise to steady-state phase transitions. A common strategy is to embed the system-environment into a larger unitary framework, but this obscures the intrinsic complexity of the reduced system dynamics. Here, we investigate the computational complexity of simulating open quantum systems, focusing on two physically relevant parameters -- correlation length and mixing time -- and explore whether it can be comparable (or even lower) to that of simulating their closed counterparts. In particular, we study the role of dissipation in simulating open-system dynamics using both quantum and classical methods, where the classical complexity is characterised by the bond dimension and operator entanglement entropy. Our results show that dissipation affects correlation length and mixing time in distinct ways at intermediate and long timescales. Moreover, we observe numerically that in classical tensor network simulations, classical complexity does not decrease with stronger dissipation, revealing a separation between quantum and classical resource scaling. + oai:arXiv.org:2508.19959v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + physics.comp-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - 10.1088/2058-9565/ae2885 - Danilo Triggiani, Cosmo Lupo + Lucia Vilchez-Estevez, Alexander Yosifov, Jinzhao Sun - Optimizing the non-Clifford-count in unitary synthesis using Reinforcement Learning - https://arxiv.org/abs/2509.21709 - arXiv:2509.21709v2 Announce Type: replace -Abstract: In this paper we study the potential of using reinforcement learning (RL) in order to synthesize quantum circuits, while optimizing the T-count and CS-count, of unitaries that are exactly implementable by the Clifford+T and Clifford+CS gate sets, respectively. We have designed our RL framework to work with channel representation of unitaries, that enables us to perform matrix operations efficiently, using integers only. We have also incorporated pruning heuristics and a canonicalization of operators, in order to reduce the search complexity. As a result, compared to previous works, we are able to implement significantly larger unitaries, in less time, with much better success rate and improvement factor. Our results for Clifford+T synthesis on two qubit unitaries achieve close-to-optimal decompositions for up to 100 T gates, 5 times more than previous RL algorithms and to the best of our knowledge, the largest instances achieved with any method to date. Our RL algorithm is able to recover previously-known optimal linear complexity algorithm for T-count-optimal decomposition of 1 qubit unitaries. We illustrate significant reduction in the asymptotic T-count estimate of important primitives like controlled cyclic shift (43%), controlled adder (14.3%) and multiplier (14%), without adding any extra ancilla. For 2-qubit Clifford+CS unitaries, our algorithm achieves a linear complexity, something that could only be accomplished by a previous algorithm using SO(6) representation. - oai:arXiv.org:2509.21709v2 + Direct measurement of the quantum geometric tensor in pseudo-Hermitian systems + https://arxiv.org/abs/2509.17043 + arXiv:2509.17043v2 Announce Type: replace +Abstract: The quantum geometric tensor (QGT) fundamentally encodes the geometry and topology of quantum states in both Hermitian and non-Hermitian regimes. While adiabatic perturbation theory links its real part (quantum metric) and imaginary part (Berry curvature) to energy fluctuations and generalized forces, respectively, in Hermitian systems, direct measurement of the QGT, which is defined using both left and right eigenstates of a non-Hermitian Hamiltonian, remains challenging. Here we develop two quantum simulation schemes to directly extract all components of the QGT in pseudo-Hermitian systems with real spectra. Each scheme independently determines the complete QGT using generalized expectation values of either the energy fluctuation operator or the generalized force operator with respect to two time-evolved states prepared through distinct nonadiabatic evolutions, thereby establishing two self-contained measurement protocols. We illustrate the validity of these schemes on two $q$-deformed two-band models: one with nontrivial topology and the other with a nonvanishing off-diagonal quantum metric. Numerical simulations demonstrate that, for suitably chosen nonadiabatic ramp velocities, both schemes achieve high-fidelity agreement with theoretical predictions for measuring the QGT in both models and successfully capture the topological phase transition of the first model using Chern numbers calculated from Berry curvatures. For larger velocities, the generalized force scheme yields greater accuracy for the real part of the QGT, while the energy fluctuation scheme better captures its imaginary part. This work establishes a framework for extending dynamical measurement schemes from Hermitian to pseudo-Hermitian systems with real spectra. + oai:arXiv.org:2509.17043v2 quant-ph - cs.AI - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/x8tj-bhwz + Phys. Rev. A 112, 062225 (2025) + Ze-Hao Huang, Hai-Tao Ding, Li-Jun Lang + + + Frame dependence of Spekkens' contextuality for relativistic spin systems + https://arxiv.org/abs/2509.17967 + arXiv:2509.17967v2 Announce Type: replace +Abstract: We show that the operational definition of contextuality introduced by Spekkens is, in general, not Lorentz invariant. Specifically, we consider an explicit example with particle states consisting of both spin and momentum, we apply a Lorentz transformation to obtain the states in a new inertial frame, and then trace out the momentum degrees of freedom in both frames. We find that, while an observer in the first inertial frame describes a contextual ontological model with respect to spin states and all possible spin measurements, an observer in the boosted frame describes a non-contextual model with respect to the transformed spin states and all transformed spin measurements. Hence, the Spekkens' notion of contextuality, when restricted to spin degress of freedom only, is a frame-dependent concept. We apply our results to predict a novel relativistic effect concerning the task of discriminating between two quantum states. We show that the probability of success for a moving observer exceeds that of an observer at rest. + oai:arXiv.org:2509.17967v2 + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - David Kremer, Ali Javadi-Abhari, Priyanka Mukhopadhyay + Ruben Campos Delgado + + + The NPA hierarchy does not always attain the commuting operator value + https://arxiv.org/abs/2510.04943 + arXiv:2510.04943v4 Announce Type: replace +Abstract: We show that it is undecidable to determine whether the commuting operator value of a nonlocal game is strictly greater than 1/2. Specifically, there is a computable mapping from Turing machines to /boolean constraint system (BCS) nonlocal games in which the halting property of the machine is encoded as a decision problem for the commuting operator value of the game. As a corollary, there is a BCS game for which the value of the Navascu\'es-Pironio-Ac\'in (NPA) hierarchy does not attain the commuting operator value at any finite level. + oai:arXiv.org:2510.04943v4 + quant-ph + cs.CC + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Marco Fanizza, Larissa Kroell, Arthur Mehta, Connor Paddock, Denis Rochette, William Slofstra, Yuming Zhao - Exact Quantum Stochastic Differential Equations for Reverse Diffusion - https://arxiv.org/abs/2511.15919 - arXiv:2511.15919v3 Announce Type: replace -Abstract: The ensemble-averaged dynamics of open quantum systems are typically irreversible. We show that this irreversibility need not hold at the level of individually monitored quantum trajectories. Our main results are analytical quantum stochastic differential equations for reverse diffusion, along with corresponding stochastic master equations. These equations describe the exact and approximate stochastic reverse processes for continuously monitored Pauli channels, including time-dependent depolarizing noise. We show that the reverse processes generalize the forward dynamics by combining the noise effects of the forward processes with an additional non-Markovian stochastic drift that dynamically steers a quantum state back to its initial configuration. Consequently, the exact SDEs admit closed-form solutions that can be implemented in real-time without the need for variational techniques. Our findings establish an analytical framework for quantum state recovery, noise-resilient quantum gates, quantum generative modelling, quantum tomography via forward-reverse cycles, and potential paradigms for quantum error correction based on reverse diffusion. - oai:arXiv.org:2511.15919v3 + Quantum Mechanics Relative to a Quantum Reference System: a Relative State Approach + https://arxiv.org/abs/2510.17513 + arXiv:2510.17513v2 Announce Type: replace +Abstract: This paper proposes an intrinsic or background-independent quantum framework based on entangled state rather than absolute quantum state, it describes a quantum relative state between the under-study quantum system and the quantum measuring apparatus as a quantum reference system, without relying on any external absolute parameter. The paper focuses on a simple example, in which a quantum object's one-dimensional position as an under-study quantum system, and a quantum clock as a quantum reference system or quantum measuring apparatus. The evolution equation of the state of the quantum object's position with respect to the state of the quantum clock is given coming from the Ricci-flat Kaehler-Einstein equation. In a linear and non-relativistic approximation, the framework recovers the equation of the standard quantum mechanics, in which an intrinsic potential related to some "inertial force" is automatically incorporated in the covariant derivative. A physical relative probability interpretation and a geometric non-trivial fiber bundle interpretation of the entangled state in this intrinsic quantum framework are given. Furthermore, some non-inertial effects, such as the "inertial force", coming from the general covariance of the intrinsic quantum framework are also discussed. Compared with the functional integral approach which is more easily to generalize the quantum clock to the quantum spacetime reference frame and study quantum gravity, the relative state approach as a canonical description is more suitable for conceptually demonstrating the connections to the standard formalism and interpretation of the quantum mechanics. + oai:arXiv.org:2510.17513v2 quant-ph + gr-qc math-ph math.MP - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Einar Gabbassov + M. J. Luo - Unified Bulk-Entanglement Correspondence in Non-Hermitian Systems - https://arxiv.org/abs/2511.17846 - arXiv:2511.17846v2 Announce Type: replace -Abstract: The non-Hermitian skin effect (NHSE) fundamentally invalidates the conventional bulk-boundary correspondence (BBC), leading topological diagnostics into a crisis. While the non-Bloch polarization $P_{\beta}$ defined on the generalized Brillouin zone restores momentum-space topology, a direct, robust real-space bulk probe has remained elusive. We resolve this by establishing a universal correspondence between $P_{\beta}$ and the entanglement polarization $\chi$ of the biorthogonal ground state. Introducing a quasi-reciprocal Hamiltonian $\tilde{H}$ that removes the NHSE while preserving bulk topology, we rigorously prove the fundamental identity $P_{\beta} \equiv \chi(\tilde{H})\pmod 1$ in the thermodynamic limit under the quasi-locality assumption. Crucially, we demonstrate that this equivalence transcends the locality constraints that limit traditional topological invariants. While the conventional Resta polarization fails when $\tilde{H}$ becomes non-local due to the divergence of position variance, we reveal that $\chi(\tilde{H})$ remains robustly quantized, protected by the Fredholm index of Toeplitz operators. Our work thus identifies entanglement as the unique real-space diagnostic capable of capturing non-Bloch topology beyond the breakdown of locality, successfully restoring the BBC across diverse non-Hermitian systems such as line-gap, point-gap, and gapless phases, thereby unifying the geometric and entanglement paradigms in non-Hermitian physics. - oai:arXiv.org:2511.17846v2 + Superconducting pairing correlations on a trapped-ion quantum computer + https://arxiv.org/abs/2511.02125 + arXiv:2511.02125v2 Announce Type: replace +Abstract: The Fermi-Hubbard model is the starting point for the simulation of many strongly correlated materials, including high-temperature superconductors, whose modelling is a key motivation for the construction of quantum simulation and computing devices. However, the detection of superconducting pairing correlations has so far remained out of reach, both because of their off-diagonal character - which makes them inaccessible to local density measurements - and because of the difficulty of preparing superconducting states. Here, we report measurement of significant pairing correlations in three different regimes of Fermi-Hubbard models simulated on Quantinuum's Helios trapped-ion quantum computer. Specifically, we measure non-equilibrium pairing induced by an electromagnetic field in the half-filled square lattice model, d-wave pairing in an approximate ground state of the checkerboard Hubbard model at $1/6$-doping, and s-wave pairing in a bilayer model relevant to nickelate superconductors. These results show that a quantum computer can reliably create and probe physically relevant states with superconducting pairing correlations, opening a path to the exploration of superconductivity with quantum computers. + oai:arXiv.org:2511.02125v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.str-el + cond-mat.supr-con + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xudong Zhang, Zhaoyu Sun, Bin Guo + Etienne Granet, Sheng-Hsuan Lin, Kevin H\'emery, Reza Hagshenas, Pablo Andres-Martinez, David T. Stephen, Anthony Ransford, Jake Arkinstall, M. S. Allman, Pete Campora, Samuel F. Cooper, Robert D. Delaney, Joan M. Dreiling, Brian Estey, Caroline Figgatt, Cameron Foltz, John P. Gaebler, Alex Hall, Ali Husain, Akhil Isanaka, Colin J. Kennedy, Nikhil Kotibhaskar, Ivaylo S. Madjarov, Michael Mills, Alistair R. Milne, Annie J. Park, Adam P. Reed, Brian Neyenhuis, Justin G. Bohnet, Michael Foss-Feig, Andrew C. Potter, Ramil Nigmatullin, Mohsin Iqbal, Henrik Dreyer - Quantum Encrypted Control of Networked Systems - https://arxiv.org/abs/2512.03434 - arXiv:2512.03434v2 Announce Type: replace -Abstract: Encrypted control has been extensively studied to ensure the confidentiality of system states and control inputs for networked control systems. This paper presents a computationally efficient encrypted control framework for networked systems enabled by quantum communication. A quantum channel between sensors and actuators is used to generate identical secret keys, whose security is further enhanced through quantum key distribution. These keys enable lightweight encryption and decryption while preserving confidentiality and control accuracy. We develop a novel encryption-decryption architecture for state-feedback control of linear systems based on quantum keys, and characterize the impact of quantum state errors on closed-loop stability. In particular, we establish the existence of a critical threshold on intrinsic quantum noise below which stability is guaranteed. In contrast to classical encrypted control schemes, which may collapse under a single key-bit error, the proposed quantum encrypted control exhibits strong robustness to key imperfections. We further adopt quantization techniques to address the scenarios with limited communication bits in practical situations, and implement privacy protection for quantum keys based on a stochastic quantizer. These results demonstrate that integrating quantum technologies into control systems in a nontrivial and principled manner, even at their current level of maturity, can yield substantial performance gains in reducing computational complexity and improving resilience to key errors while ensuring security against multiple eavesdropping sources. - oai:arXiv.org:2512.03434v2 + Tight Analysis of a One-Shot Quantum Secret Sharing Scheme + https://arxiv.org/abs/2511.04399 + arXiv:2511.04399v2 Announce Type: replace +Abstract: Quantum communication protocols can be designed to detect eavesdropping attacks, something that classical technologies are unable to do since classical information can be replicated in a non-destructive manner. Eavesdropping detection is, therefore, a standard feature in all the proposed quantum secret sharing (QSS) protocols. However, detection is often done by a statistical analysis of the outcome of multiple decoy rounds, and this causes a significant communication overhead. + In our quest for a QSS protocol that works even in one round, we came across a one-shot secret-sharing framework proposed by Hsu (Phys. Rev. A 2003). The scheme was designed to work over public channels without requiring multiple rounds to detect eavesdropping but it lacked a thorough security analysis. In this work we present a complete characterisation of the correctness and security properties of this framework. Our characterisation allowed us to improve the original protocol to be more resistant towards eavesdropping. However, we prove a couple of impossibility results, including one that dictates that complete security against an eavesdropper is not possible in this framework. Thus, it is not possible to design a perfect QSS using this framework. + oai:arXiv.org:2511.04399v2 quant-ph - cs.SY - eess.SY - Fri, 12 Dec 2025 00:00:00 -0500 + cs.CR + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zihao Ren, Daniel Quevedo, Salah Sukkarieh, Guodong Shi + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Santanu Majhi, Debajyoti Bera - Practical protein-pocket hydration-site prediction for drug discovery on a quantum computer - https://arxiv.org/abs/2512.08390 - arXiv:2512.08390v2 Announce Type: replace -Abstract: Demonstrating the practical utility of Noisy Intermediate-Scale Quantum (NISQ) hardware for recurrent tasks in Computer-Aided Drug Discovery is of paramount importance. We tackle this challenge by performing three-dimensional protein pockets hydration-site prediction on a quantum computer. Formulating the water placement problem as a Quadratic Unconstrained Binary Optimization (QUBO), we use a hybrid approach coupling a classical three-dimensional reference-interaction site model (3D-RISM) to an efficient quantum optimization solver, to run various hardware experiments up to 123 qubits. Matching the precision of classical approaches, our results reproduced experimental predictions on real-life protein-ligand complexes. Furthermore, through a detailed resource estimation analysis, we show that accuracy can be systematically improved with increasing number of qubits, indicating that full quantum utility is in reach. Finally, we provide evidence that advantageous situations could be found for systems where classical optimization struggles to provide optimal solutions. The method has potential for assisting simulations of protein-ligand complexes for drug lead optimization and setup of docking calculations. - oai:arXiv.org:2512.08390v2 + Room-Temperature Electrical Readout of Spin Defects in van der Waals Materials + https://arxiv.org/abs/2511.08874 + arXiv:2511.08874v2 Announce Type: replace +Abstract: Negatively charged boron vacancy ($\mathrm{V_B^-}$) in hexagonal boron nitride (hBN) is the most extensively studied room-temperature quantum spin system in two-dimensional (2D) materials. Nevertheless, the current effective readout of $\mathrm{V_B^-}$ spin states is carried out by systematically optical methods. This limits their exploitation in compact and miniaturized quantum devices, which would otherwise hold substantial promise to address quantum sensing and quantum information tasks. In this study, we demonstrated a photoelectric spin readout technique for $\mathrm{V_B^-}$ spins in hBN. The observed photocurrent signals stem from the spin-dependent ionization dynamics of boron vacancies, mediated by spin-dependent non-radiative transitions to a metastable state. We further extend this electrical detection technique to enable the readout of dynamical decoupling sequences, including the Carr-Purcell-Meiboom-Gill (CPMG) protocols, and of nuclear spins via electron-nuclear double resonance. These results provide a pathway toward on-chip integration and real-field exploitation of quantum functionalities based on 2D material platforms. + oai:arXiv.org:2511.08874v2 quant-ph - physics.bio-ph - physics.chem-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - Daniele Loco, Kisa Barkemeyer, Andre R. R. Carvalho, Jean-Philip Piquemal + http://creativecommons.org/licenses/by-nc-sa/4.0/ + 10.1103/dlzw-dhsr + Physical Review Letters 135, 220802 (2025) + Shihao Ru, Liheng An, Haidong Liang, Zhengzhi Jiang, Zhiwei Li, Xiaodan Lyu, Feifei Zhou, Hongbing Cai, Yuzhe Yang, Ruihua He, Robert Cernansky, Edwin Hang Tong Teo, Manas Mukherjee, Andrew A. Bettiol, Jesus Z\'u\~niga-Perez, Fedor Jelezko, Weibo Gao - High-OAM Deep Ultraviolet Twisted Light Generation for RF-Photoinjector Applications - https://arxiv.org/abs/2512.08442 - arXiv:2512.08442v3 Announce Type: replace -Abstract: We report on the generation and characterization of ultraviolet (wavelength 266 nm) twisted light with high orbital angular momentum (OAM) using three types of fabricated diffractive optical elements (DOEs): a reflective fork grating, a high-charge spiral phase plate (SPP), and binary axicons. All elements were integrated into a drive-laser beamline of an electron RF-photoinjector, enabling direct evaluation under accelerator-relevant conditions. The SPP produced a high-purity Laguerre-Gaussian mode with OAM l = 64 and a measured conversion efficiency of approximately 80%. Binary axicons generated quasi-Bessel twisted light with topological charges up to m = 10, exhibiting low divergence and stable multi-lobe ring structures. The fork grating reliably produced lower-order modes, l = 2-8, with good agreement between simulations and cylindrical-lens diagnostics. These results constitute, to our knowledge, the first comprehensive experimental demonstration of deep-UV high-OAM beams generated with fabricated DOEs and validated through mode-conversion measurements. The demonstrated techniques are compatible with high-power UV laser systems used in RF-photoinjectors and offer a practical route toward structured photocathode illumination and the generation of relativistic vortex electrons at a particle accelerator facility. - oai:arXiv.org:2512.08442v3 + On-Demand Control of Input-State-Dependent Single-Photon Scattering in Multi-Mode Waveguides + https://arxiv.org/abs/2511.22840 + arXiv:2511.22840v2 Announce Type: replace +Abstract: Precise control of a single photon transport in broadband, multi-mode waveguides is a fundamental challenge for scalable quantum networks. We propose a theoretical scheme for on-demand control of single-photon scattering using a driven $\Lambda$-type emitter coupled to a rectangular waveguide. By employing the Lippmann-Schwinger formalism, we derive the exact analytical scattering matrix and reveal two key interference mechanisms: electromagnetically induced transparency for complete transmission and Fano resonance for complete reflection. We demonstrate that the single-photon scattering is dynamically engineered by the driving field, enabling a switch between complete transmission and dual-frequency complete reflection. Crucially, in the multi-mode regime, we show that the scattering is governed by quantum interference between modes, making it critically dependent on the input photonic state. By preparing the photon in a specific coherent superposition state, the multi-mode interference is harnessed to achieve Fano resonance-mediated complete reflection. Conversely, a single-mode input suppresses complete reflection. This input-state-dependent scattering establishes a general framework for multi-mode quantum photonics, paving the way for broadband dual-frequency filters, multi-mode quantum routers, and on-chip spectrometers. + oai:arXiv.org:2511.22840v2 quant-ph - physics.acc-ph - physics.optics - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Yan Liu, Qing-Ao Xiang, Xin-Yuan Yang, Ji-Bing Yuan, Shi-Qing Tang, Xin-Wen Wang, Ya-Ju Song + + + Folded optimal transport and its application to separable quantum optimal transport + https://arxiv.org/abs/2512.01722 + arXiv:2512.01722v2 Announce Type: replace +Abstract: We introduce folded optimal transport, as a way of extending a cost or distance defined on the extreme boundary of a convex to the whole convex, related to convex extension. This construction broadens the framework of standard optimal transport, found to be the particular case of the convex being a simplex. Relying on Choquet theory and standard optimal transport, we introduce the so-called folded Kantorovich cost and folded Wasserstein distance, and study the metric properties it provides to the convex. We then apply the construction to the quantum setting, and obtain an actual separable quantum Wasserstein distance on the set of density matrices from a distance on the set of pure states, closely related to the semi-distance of Beatty and Stilck-Franca [4], and of which we obtain a variety of properties. We also find that the semiclassical Golse-Paul [16] cost writes as a folded Kantorovich cost. Folded optimal transport therefore provides a unified framework for classical, semiclassical and separable quantum optimal transport. + oai:arXiv.org:2512.01722v2 + quant-ph + math-ph + math.FA + math.MP + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - A. S. Dyatlov, D. M. Dolgintsev, V. V. Gerasimov, V. V. Kobets, V. P. Nazmov, M. A. Nozdrin, A. N. Sergeev, D. S. Shokin, K. E. Yunenko, D. V. Karlovets + Thomas Borsoni - Higher Josephson harmonics in a tunable double-junction transmon qubit - https://arxiv.org/abs/2512.08470 - arXiv:2512.08470v2 Announce Type: replace -Abstract: Tunable Josephson harmonics open new avenues for qubit design. We demonstrate a superconducting circuit element consisting of a tunnel junction in series with a SQUID loop, yielding a Josephson potential whose harmonic content is strongly tunable by magnetic flux. Through spectroscopy of the first four qubit transitions, together with an effective single-mode model renormalized by the internal mode, we resolve a second harmonic with an amplitude up to $\sim10\%$ of the fundamental. We identify a flux sweet spot where the dispersive shift vanishes, achieved by balancing the dispersive couplings to the internal and qubit modes. This highly tunable element provides a route toward protected qubits and customizable nonlinear microwave devices. - oai:arXiv.org:2512.08470v2 + Polylogarithmic-Depth Quantum Algorithm for Simulating the Extended Hubbard Model on a Two-Dimensional Lattice Using the Fast Multipole Method + https://arxiv.org/abs/2512.03898 + arXiv:2512.03898v4 Announce Type: replace +Abstract: The extended Hubbard model on a two-dimensional lattice captures key physical phenomena, but is challenging to simulate due to the presence of long-range interactions. In this work, we present an efficient quantum algorithm for simulating the time evolution of this model. Our approach, inspired by the fast multipole method, approximates pairwise interactions by interactions between hierarchical levels of coarse-graining boxes. We discuss how to leverage recent advances in two-dimensional neutral atom quantum computing, supporting non-local operations such as long-range gates and shuttling. The resulting circuit depth for a single Trotter step scales polylogarithmically with system size. + oai:arXiv.org:2512.03898v4 quant-ph - cond-mat.mes-hall - Fri, 12 Dec 2025 00:00:00 -0500 + cond-mat.str-el + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Ksenia Shagalov, David Feldstein-Bofill, Leo Uhre Jakobsen, Zhenhai Sun, Casper Wied, Amalie T. J. Paulsen, Johann Bock Severin, Malthe A. Marciniak, Clinton A. Potts, Anders Kringh{\o}j, Jacob Hastrup, Karsten Flensberg, Svend Kr{\o}jer, Morten Kjaergaard + Yu Wang, Martina Nibbi, Maxine Luo, Isabel Nha Minh Le, Yanbin Chen, J. Ignacio Cirac, Christian B. Mendl - Certified Private Quantum Time Ticks Away Faster than Any Classical Clock - https://arxiv.org/abs/2512.09100 - arXiv:2512.09100v2 Announce Type: replace -Abstract: We introduce the concept of an entangled clock, where the flow of time is operationally defined by the discrete registration of measurement outcomes on a singlet state. Comparing the synchronization rate of two such clocks against classical models, we find that at obtuse relative angles, the quantum clock ticks strictly faster than this classical benchmark. We further propose a protocol for Certified Private Time, adapting device-independent randomness certification to the temporal domain; this guarantees a sovereign timeline that ticks away faster than any local realistic mechanism allows. - oai:arXiv.org:2512.09100v2 + Exponentially accelerated relaxation and quantum Mpemba effect in open quantum systems + https://arxiv.org/abs/2512.07561 + arXiv:2512.07561v2 Announce Type: replace +Abstract: We investigate the quantum Mpemba effect in the relaxation of open quantum systems whose effective dynamics is described by Davies maps. We present a class of unitary transformations built from permutation matrices that, when applied to the initial state of the system, (i) suppress the slowest decaying modes of the nonunitary dynamics; (ii) maximize its distinguishability from the steady state. The first requirement guarantees exponentially accelerating convergence to the steady state, and the second implies that a quantum system initially farther from equilibrium approaches it more rapidly than one that starts closer. This protocol provides a genuine Mpemba effect, and its numerical simulation requires low computational effort. We prove that, for any initial state, one can always find a permutation matrix that maximizes its distance from equilibrium for a specified information-theoretic distinguishability measure. We illustrate our findings for a two-level system, and also for the nonunitary dynamics of the transverse field Ising chain and XXZ chain, each weakly coupled to a bosonic thermal bath, and demonstrate the quantum Mpemba effect as captured by the Hilbert-Schmidt distance, quantum relative entropy, and trace distance. Our results provide a versatile framework to engineer the genuine quantum Mpemba effect in Markovian open quantum systems. + oai:arXiv.org:2512.07561v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Karl Svozil + Emerson Lima Caldas, Diego Paiva Pires - Spontaneous Decoherence from Imaginary-Order Spectral Deformations - https://arxiv.org/abs/2512.09236 - arXiv:2512.09236v2 Announce Type: replace -Abstract: A mechanism of spontaneous decoherence is examined in which the generator of quantum dynamics is replaced by the imaginary-order (which is fundamentally different from real-order fractional calculus) spectral deformation $H^{1+i\beta}$ for a positive self-adjoint Hamiltonian $H$. The deformation modifies dynamical phases through the factor $E^{i\beta}=e^{i\beta\log E}$, whose rapid oscillation suppresses interference between distinct energies. A non-stationary-phase analysis yields quantitative estimates: oscillatory contributions to amplitudes or decoherence functionals decay at least as $\mathcal{O}(1/|\beta|)$. The kinematical structure of quantum mechanics -- the Hilbert-space inner product, projection operators, and the Born rule -- remains unchanged; the modification is entirely dynamical and acts only through spectral phases. - Physical motivations for the deformation arise from clock imperfections, renormalization--group and effective--action corrections that introduce logarithmic spectral terms, and semiclassical gravity analyses in which complex actions produce spectral factors of the form $E^{i\beta}$. The mechanism is illustrated in examples relevant to quantum-gravity-inspired quantum mechanics. - A detailed related-work analysis contrasts the present mechanism with Milburn-type intrinsic decoherence, Di\'osi-Penrose gravitational collapse, GRW/CSL models, clock-induced decoherence, and energy-conserving collapse models, as well as environmental frameworks such as Lindblad master equations, Caldeira-Leggett baths, and non-Hermitian Hamiltonian deformations. This positions $H^{1+i\beta}$ dynamics as a compact, testable, and genuinely novel phenomenological encapsulation of logarithmic spectral corrections arising in quantum-gravity- motivated effective theories, while remaining fully compatible with standard quantum kinematics. - oai:arXiv.org:2512.09236v2 + Generative Adversarial Variational Quantum Kolmogorov-Arnold Network + https://arxiv.org/abs/2512.11014 + arXiv:2512.11014v2 Announce Type: replace +Abstract: Kolmogorov Arnold Networks is a novel multilayer neuromorphic network that can exhibit higher accuracy than a neural network. It can learn and predict more accurately than neural networks with a smaller number of parameters, and many research groups worldwide have adopted it. As a result, many types of applications have been proposed. This network can be used as a generator solely or with a Generative Adversarial Network; however, KAN has a slower speed of learning than neural networks for the number of parameters. Hence,it has not been researched as a generator. Therefore, we propose a novel Generative Adversarial Network called Generative Adversarial Variational Quantum KAN that uses Variational Quantum KAN as a generator. This method enables efficient learning with significantly fewer parameters by leveraging the computational advantages of quantum circuits and their output distributions. We performed the training and generation task on MNIST and CIFAR10, and revealed that our method can achieve higher accuracy than neural networks and Quantum Generative Adversarial Network with less data. + oai:arXiv.org:2512.11014v2 quant-ph - gr-qc - hep-th - math-ph - math.MP - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Sridhar Tayur + Hikaru Wakaura - Topological aspects of periodically driven non-Hermitian Su-Schrieffer-Heeger model - https://arxiv.org/abs/2011.06947 - arXiv:2011.06947v3 Announce Type: replace-cross -Abstract: A non-Hermitian generalization of the Su-Schrieffer-Heeger model driven by a periodic external potential is investigated, and its topological features are explored. We find that the bi-orthonormal geometric phase acts as a topological index, well capturing the presence/absence of the zero modes. The model is observed to display trivial and non-trivial insulator phases and a topologically non-trivial M${\"o}$bius metallic phase. The driving field amplitude is shown to be a control parameter causing topological phase transitions in this model. While the system displays zero modes in the metallic phase apart from the non-trivial insulator phase, the metallic zero modes are not robust, as the ones found in the insulating phase. We further find that zero modes' energy converges slowly to zero as a function of the number of dimers in the M${\"o}$bius metallic phase compared to the non-trivial insulating phase. - oai:arXiv.org:2011.06947v3 - cond-mat.mes-hall + Expected values for SUSY hierarchies of Jaynes-Cummings Hamiltonian + https://arxiv.org/abs/2512.12647 + arXiv:2512.12647v2 Announce Type: replace +Abstract: The aim of this letter is to compute the evolution of some expected values, such as the field operators $a^{\pm}$, quadratures and atomic inversion, under SUSY partner Hamiltonians associated to the Jaynes-Cummings Hamiltonian of quantum optics. This kind of SUSY partners are characterized by having spectra which differ in a finite number of energy levels. We wish to elucidate if the partner connection has any influence on these expected values. In particular, we want also to know in which way the classical and revival times are affected by such SUSY partners. + oai:arXiv.org:2512.12647v2 + quant-ph math-ph math.MP + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + \.Ismail Burak Ate\c{s}, \c{S}eng\"ul Kuru, Javier Negro, Ege \"Ozkan + + + Matter-Mediated Entanglement in Classical Gravity: Suppression by Binding Potentials and Localization + https://arxiv.org/abs/2512.13675 + arXiv:2512.13675v2 Announce Type: replace +Abstract: Aziz and Howl [Nature 646 (2025)] argue that two spatially separated masses can become entangled even when gravity is treated as a classical field, by invoking higher-order "virtual-matter" processes in a QFT description of matter, which is non-LOCC (local operations and classical communication). We point out that the relevant mechanism is not intrinsically field-theoretic, but is essentially a quantum tunneling/evanescent matter channel, which is already captured within ordinary quantum mechanics. More importantly, the microscopic constituents of realistic macroscopic objects are bound and localized by strong potentials, introducing a large internal energy scale that suppresses coherent propagation between distant bodies. Including such binding/localization generically yields an exponential suppression, rendering the matter-mediated contribution negligible at the macroscopic separations relevant to gravitational-entanglement proposals. Consequently, the entanglement identified by AH diagnoses the presence of a coherent matter-exchange channel rather than the classical or quantum nature of gravity, and it does not undermine LOCC-based witness arguments in realistic bound-matter platforms. + oai:arXiv.org:2512.13675v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 - replace-cross + Fri, 19 Dec 2025 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - 10.1103/PhysRevB.103.075441 - Phys. Rev. B 103, 075441 (2021) - Vivek M. Vyas, Dibyendu Roy + Ziqian Tang, Chen Yang, Zizhao Han, Zikuan Kan, Yulong Liu, Hanyu Xue - Unconditional correctness of recent quantum algorithms for factoring and computing discrete logarithms - https://arxiv.org/abs/2404.16450 - arXiv:2404.16450v2 Announce Type: replace-cross -Abstract: In 1994, Shor introduced his famous quantum algorithm to factor integers and compute discrete logarithms in polynomial time. In 2023, Regev proposed a multi-dimensional version of Shor's algorithm that requires far fewer quantum gates. His algorithm relies on a number-theoretic conjecture on the elements in $(\mathbb{Z}/N\mathbb{Z})^{\times}$ that can be written as short products of very small prime numbers. We prove a version of this conjecture using tools from analytic number theory such as zero-density estimates. As a result, we obtain an unconditional proof of correctness of this improved quantum algorithm and of subsequent variants. - oai:arXiv.org:2404.16450v2 - math.NT - cs.CC + Extreme non-negative Wigner functions + https://arxiv.org/abs/2512.14831 + arXiv:2512.14831v2 Announce Type: replace +Abstract: Providing an operational characterization of the Wigner-positive states (WPS), i.e., the set of quantum states with non-negative Wigner function, is a longstanding open problem. For pure states, the only WPS are Gaussian states, but the situation is considerably more subtle for mixed states. Here, we approach the problem using convex geometry, reducing the question to the characterization of the extreme points of the set of WPS. We give a constructive method to generate a large class of such extreme WPS, which combines the following steps: (i) we characterize the phase-invariant extreme points of the superset of Wigner-positive quasi-states (WPQS); (ii) we introduce a new quantum map, named Vertigo map, which maps extreme WPQS to extreme WPS while preserving phase invariance; (iii) we identify families of extremality-preserving maps and use them to obtain extreme WPS while relaxing phase invariance. Our construction generates all extreme WPS of low dimension, starting from a specific kind of WPS known as beam-splitter states. Our results build upon new mathematical properties of the set of WPS derived in a companion paper and unveil the remarkable structure of mixed states with non-negative Wigner functions. + oai:arXiv.org:2512.14831v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 - replace-cross + Fri, 19 Dec 2025 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - C\'edric Pilatte + Zacharie Van Herstraeten, Jack Davis, Nuno C. Dias, Jo\~ao N. Prata, Nicolas J. Cerf, Ulysse Chabaud - Rydberg Atomic Quantum Receivers for Multi-Target DOA Estimation - https://arxiv.org/abs/2501.02820 - arXiv:2501.02820v3 Announce Type: replace-cross -Abstract: Quantum sensing technologies have experienced rapid progresses since entering the `second quantum revolution'. Among various candidates, schemes relying on Rydberg atoms exhibit compelling advantages for detecting radio frequency signals. Based on this, Rydberg atomic quantum receivers (RAQRs) have emerged as a promising solution to classical wireless communication and sensing. To harness the advantages and exploit the potential of RAQRs in wireless sensing, we investigate the realization of the direction of arrival (DOA) estimation by RAQRs. Specifically, we first conceive a Rydberg atomic quantum uniform linear array (RAQ-ULA) aided wireless receiver for multi-target DOA detection and propose the corresponding signal model of this sensing system. Our model reveals that the presence of the radio-frequency local oscillator in the RAQ-ULA creates sensor gain mismatches, which degrade the DOA estimation significantly by employing the classical Estimation of Signal Parameters via Rotational Invariant Techniques (ESPRIT). To solve this sensor gain mismatch problem, we propose the Rydberg atomic quantum ESPRIT (RAQ-ESPRIT) relying on our model. Lastly, we characterize our scheme through numerical simulations, where the results exhibit that it is capable of reducing the estimation error of its classical counterpart on the order of $> 400$-fold and $> 9000$-fold in the PSL and SQL, respectively. - oai:arXiv.org:2501.02820v3 - eess.SP - cs.IT - math.IT + Combinatorial structures in quantum correlation: A new perspective + https://arxiv.org/abs/2512.15686 + arXiv:2512.15686v2 Announce Type: replace +Abstract: Graph-theoretic structures play a central role in the description and analysis of quantum systems. In this work, we introduce a new class of quantum states, called $A_\alpha$-graph states, which are constructed from either unweighted or weighted graphs by taking the normalised convex combination of the degree matrix $D$ and the adjacency matrix $A_G$ of a graph $G$. The constructed states are different from the standard graph states arising from stabiliser formalism. Our approach is also different from the approach used by Braunstein et al. This class of states depend on a tunable mixing parameter $\alpha \in (0,1]$. We first establish the conditions under which the associated operator $\rho_\alpha^{A_G}$ is positive semidefinite and hence represents a valid quantum state. We then derive a positive partial transposition (PPT) condition for $A_{\alpha}$-graph states in terms of graph parameters. This PPT condition involves only the Frobenius norm of the adjacency matrix of the graph, the degrees of the vertices and the total number of vertices. For simple graphs, we obtain the range of the parameter $\alpha$ for which the $A_{\alpha}$-graph states represent a class of entangled states. We then develop a graph-theoretic formulation of a moments-based entanglement detection criterion, focusing on the recently proposed $p_3$-PPT criterion, which relies on the second and third moments of the partial transposition. Since the estimation of these moments is experimentally accessible via randomised measurements, swap operations, and machine-learning-based protocols, our approach provides a physically relevant framework for detecting entanglement in structured quantum states derived from graphs. This work bridges graph theory and moments-based entanglement detection, offering a new perspective on the role of combinatorial structures in quantum correlations. + oai:arXiv.org:2512.15686v2 quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Rohit kumar, Satyabrata Adhikari + + + Topological materials with extensive flat-band surface states + https://arxiv.org/abs/2308.06033 + arXiv:2308.06033v3 Announce Type: replace-cross +Abstract: Materials that have zero-energy flat band states on the surface may show surface superconductivity. Here we report a theoretical observation that a Hamiltonian describing a thin slab of topological nodal line semimetal, has zero energy eigenstate spanning the entire surface of the Brillouin zone under certain conditions, namely (i) the hopping amplitude of fermions in the direction of thickness is more than that in other directions (ii) the onsite energy should be less than some limiting value determined by the hopping probability. Our claim is substantiated by analytic and numerical approach. We also report new phase transitions in a region of parameter space and indicate that the Hamiltonian can also be realised by stacked layers described by a suitable Hamiltonian. + oai:arXiv.org:2308.06033v3 + cond-mat.stat-mech + cond-mat.str-el + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Tierui Gong, Chau Yuen, Chong Meng Samson See, M\'erouane Debbah, Lajos Hanzo + 10.1088/1361-648X/ae2818 + Protyush Nandi and Subinay Dasgupta 2026 J. Phys.: Condens. Matter 38 015401 + Protyush Nandi, Subinay Dasgupta - Generation of Deep Ultraviolet Optical Vortices via Amplitude and Phase Spiral Zone Plates - https://arxiv.org/abs/2501.16950 - arXiv:2501.16950v3 Announce Type: replace-cross -Abstract: We present the development and experimental implementation of diffractive optical elements designed to generate optical vortices in the deep ultraviolet range (from 260 to 266 nm). These elements, fabricated using advanced lithographic and etching techniques, facilitate the efficient transformation of Gaussian beams into twisted modes carrying orbital angular momentum. Experimental tests conducted using the laser driver of an RF photoinjector at JINR successfully demonstrate the generation of deep-ultraviolet optical vortices with a topological charge of l = 1. These findings underscore the potential of structured light in the deep ultraviolet range for applications in relativistic electron beam studies and beam manipulation technologies. - oai:arXiv.org:2501.16950v3 - physics.optics - physics.acc-ph + Even-Cycle Detection in the Randomized and Quantum CONGEST Model + https://arxiv.org/abs/2402.12018 + arXiv:2402.12018v2 Announce Type: replace-cross +Abstract: We show that, for every $k\geq 2$, $C_{2k}$-freeness can be decided in $O(n^{1-1/k})$ rounds in the \CONGEST{} model by a randomized Monte-Carlo distributed algorithm with one-sided error probability $1/3$. This matches the best round-complexities of previously known algorithms for $k\in\{2,3,4,5\}$ by Drucker et al. [PODC'14] and Censor-Hillel et al. [DISC'20], but improves the complexities of the known algorithms for $k>5$ by Eden et al. [DISC'19], which were essentially of the form $\tilde O(n^{1-2/k^2})$. Our algorithm uses colored BFS-explorations with threshold, but with an original \emph{global} approach that enables to overcome a recent impossibility result by Fraigniaud et al. [SIROCCO'23] about using colored BFS-exploration with \emph{local} threshold for detecting cycles. + We also show how to quantize our algorithm for achieving a round-complexity $\tilde O(n^{\frac{1}{2}-\frac{1}{2k}})$ in the quantum setting for deciding $C_{2k}$ freeness. Furthermore, this allows us to improve the known quantum complexities of the simpler problem of detecting cycles of length \emph{at most}~$2k$ by van Apeldoorn and de Vos [PODC'22]. Our quantization is in two steps. First, the congestion of our randomized algorithm is reduced, to the cost of reducing its success probability too. Second, the success probability is boosted using a new quantum framework derived from sequential algorithms, namely Monte-Carlo quantum amplification. + oai:arXiv.org:2402.12018v2 + cs.DC quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - 10.1364/AO.578189 - A. S. Dyatlov, M. A. Nozdrin, A. N. Sergeev, N. E. Sheremet, S. S. Stafeev, D. V. Karlovets + Pierre Fraigniaud, Mael Luce, Frederic Magniez, Ioan Todinca - Quantitative imaging of nonlinear spin-wave propagation using diamond quantum sensors - https://arxiv.org/abs/2503.23321 - arXiv:2503.23321v2 Announce Type: replace-cross -Abstract: Spin waves propagating in magnetic materials exhibit nonlinear behavior at large amplitudes due to the competition between excitation and relaxation, providing an attractive platform for exploring nonlinear wave dynamics. In particular, spin waves with a non-zero wavenumber that carry momentum undergo nonlinear relaxation and experience wavenumber modulation in the nonlinear regime. This nonlinearity has been observed experimentally, for example in S. R. Lake et al., Phys. Rev. Appl. 17, 034010 (2022), but a quantitative comparison with theory has not yet been carried out. Here, We image nonlinear spin-wave propagation in two yttrium iron garnet thin films with distinct spin-wave decay rates using a wide-field quantum diamond microscope. We obtain quantitative distributions of spin-wave amplitude and phase as a function of the excitation microwave strength. As a result, we observe a threshold in the spin-wave amplitude beyond which nonlinear effects become evident and confirm that this threshold is consistent with theoretical predictions based on four-magnon scattering for both samples. Moreover, as the amplitude of the spin waves increases, we observe modulation of the wavenumber across the field of view. We attribute this modulation primarily to a reduction in the saturation magnetization caused by incoherent spin waves generated by multi-magnon scattering. Our quantitative measurements provide a pathway for visualizing nonlinear spin-wave dynamics and are crucial for deepening our understanding of the underlying mechanisms. - oai:arXiv.org:2503.23321v2 - cond-mat.mes-hall + Impact of Scalar NSI on Spatial and Temporal Correlations in Neutrino Oscillations + https://arxiv.org/abs/2411.17503 + arXiv:2411.17503v2 Announce Type: replace-cross +Abstract: Neutrino oscillation experiments are gradually approaching an era of precision, where subleading effects can also be tested. One such subleading effect is Non-Standard Interactions (NSI), which can play a crucial role in neutrino oscillations. Various works have typically discussed vector NSI in the context of quantum correlations. Recently, there have been improvements in the bounds on scalar NSI as well. In light of these developments, we aim to examine the impact of scalar NSI on quantum correlation measures. To analyze this impact, we are considering the strongest measure of quantum correlation, i.e., non-locality. Our study will encompass both spatial and temporal non-locality measures. + oai:arXiv.org:2411.17503v2 + hep-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/ys8d-cnfg - Phys. Rev. B 112, 224411 (2025) - Kensuke Ogawa, Moeta Tsukamoto, Yusuke Mori, Daigo Takafuji, Junichi Shiogai, Kohei Ueda, Jobu Matsuno, Jun-ichiro Ohe, Kento Sasaki, Kensuke Kobayashi + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1088/1361-6471/ae263c + J. Phys. G: Nucl. Part. Phys. 52 125004 (2025) + Bhavna Yadav, Ashutosh Kumar Alok - Holographic duality from Howe duality: Chern-Simons gravity as an ensemble of code CFTs - https://arxiv.org/abs/2504.08724 - arXiv:2504.08724v2 Announce Type: replace-cross -Abstract: We discuss the holographic correspondence between 3d "Chern-Simons gravity" and an ensemble of 2d Narain code CFTs. Starting from 3d abelian Chern-Simons theory, we construct an ensemble of boundary CFTs defined by gauging all possible maximal subgroups of the bulk one-form symmetry. Each maximal non-anomalous subgroup is isomorphic to a classical even self-dual error-correcting code over $\mathbb Z_p\times \mathbb Z_p$, providing a way to define a boundary "code CFT." The average over the ensemble of such theories is holographically dual to Chern-Simons gravity, a bulk theory summed over 3d topologies sharing the same boundary. In the case of prime $p$, the sum reduces to that over handlebodies, i.e. becomes the Poincar\'e series akin to that in semiclassical gravity. As the main result of the paper, we show that the mathematical identity underlying this holographic duality can be understood and rigorously proven using the framework of Howe duality over finite fields. This framework is concerned with the representation theory of two commuting groups forming a dual pair: the symplectic group of modular transformations of the boundary, and an orthogonal group mapping codes to each other. Finally, we reformulate the holographic duality as an identity between different averages over quantum stabilizer states, providing an interpretation in terms of quantum information theory. - oai:arXiv.org:2504.08724v2 - hep-th - math.RT + An Advanced Hybrid Quantum Tabu Search Approach to Vehicle Routing Problems + https://arxiv.org/abs/2501.12652 + arXiv:2501.12652v2 Announce Type: replace-cross +Abstract: Quantum computing (QC) is expected to solve incredibly difficult problems, including finding optimal solutions to combinatorial optimization problems. However, to date, QC alone is still far to demonstrate this capability except on small-sized problems. Hybrid approaches where QC and classical computing work together have shown the most potential for solving real-world scale problems. This work aims to show that we can enhance a classical optimization algorithm with QC so that it can overcome this limitation. We present a new hybrid quantum-classical tabu search (HQTS) algorithm to solve the capacitated vehicle routing problem (CVRP). Based on our prior work, HQTS leverages QC for routing within a classical tabu search framework. The quantum component formulates the traveling salesman problem (TSP) for each route as a QUBO, solved using D-Wave's Advantage system. Experiments investigate the impact of quantum routing frequency and starting solution methods. While different starting solution methods, including quantum-based and classical heuristics methods, it shows minimal overall impact. HQTS achieved optimal or near-optimal solutions for several CVRP problems, outperforming other hybrid CVRP algorithms and significantly reducing the optimality gap compared to preliminary research. The experimental results demonstrate that more frequent quantum routing improves solution quality and runtime. The findings highlight the potential of integrating QC within meta-heuristic frameworks for complex optimization in vehicle routing problems. + oai:arXiv.org:2501.12652v2 + cs.ET quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Anatoly Dymarsky, Johan Henriksson, Brian McPeak + James B. Holliday, Eneko Osaba, Khoa Luu - From hidden order to skyrmions: Quantum Hall states in an extended Hofstadter-Fermi-Hubbard model - https://arxiv.org/abs/2509.12184 - arXiv:2509.12184v2 Announce Type: replace-cross -Abstract: The interplay between topology and strong interactions gives rise to a variety of exotic quantum phases, including fractional quantum Hall (FQH) states and their lattice analogs - fractional Chern insulators (FCIs). Such topologically ordered states host fractionalized excitations and, for spinful systems, are often accompanied by ferromagnetism and skyrmions. Here, we study a Hofstadter-Hubbard model of spinful fermions on a square lattice, extended by nearest-neighbor interactions. Using large-scale density matrix renormalization group (DMRG) simulations, we demonstrate the emergence of a spin-polarized $\frac{1}{3}$-Laughlin-like FCI phase, characterized by a quantized many-body Chern number, a finite charge gap, and hidden off-diagonal long-range order. We further investigate the quantum Hall ferromagnet at $\nu=1$ and its skyrmionic excitations upon doping. In particular, we find that nearest-neighbor repulsion is sufficient to stabilize both particle- and hole-skyrmions in the ground state around $\nu=1$, whereas we do not find such textures around $\nu=\frac{1}{3}$. The diagnostic toolbox presented in this work, based on local densities, correlation functions, and spin-resolved observables, is directly applicable in quantum gas microscopy experiments. Our results open new pathways for experimental exploration of FCIs with spin textures in both ultracold atom and electronic systems. - oai:arXiv.org:2509.12184v2 - cond-mat.quant-gas + Atomic structure of the PL5 defect in silicon carbide revealed by single-spin spectroscopy and oxygen implantation + https://arxiv.org/abs/2504.07558 + arXiv:2504.07558v2 Announce Type: replace-cross +Abstract: PL5 and PL6 centers in 4H-SiC are promising for quantum applications due to their superior charge stability and optically detected magnetic resonance (ODMR) properties at room temperature. However, their atomic structures remain unresolved, with ongoing controversy regarding their potential association with stacking faults. Previous measurements relying on spin ensemble detection were insufficient to draw definitive conclusions. In this work, we conduct correlative imaging of stacking faults and PL5/PL6 at the single-defect level, definitively ruling out any spatial correlation and demonstrating that these centers are not associated with stacking faults. Furthermore, we find that substituting oxygen for nitrogen in ion implantation enhances the yields of PL5 and PL6 by more than $11$-fold and $23$-fold, respectively. Single-spin ODMR spectroscopy of PL5 reveals six distinct orientations, determines the transverse zero-field splitting parameter $E$, and characterizes the hyperfine coupling. Combined with our ab initio calculations, these results provide compelling evidence for the assignment of PL5 as an OV($kh$) defect, consisting of an oxygen atom occupying the C($k$) site as the nearest neighbor to a Si($h$) vacancy. The structural analysis together with the demonstrated defect yield enhancement lays the foundation for fabricating high-sensitivity, high-contrast ensemble quantum sensors in two and three dimensions. + oai:arXiv.org:2504.07558v2 + cond-mat.mtrl-sci cond-mat.mes-hall - cond-mat.str-el + physics.comp-ph quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Fabian J. Pauw, Ulrich Schollw\"ock, Nathan Goldman, Sebastian Paeckel, Felix A. Palm + Yu Chen, Qi Zhang, Mingzhe Liu, Junda Wu, Jinpeng Liu, Xin Zhao, Jingyang Zhou, Pei Yu, Shaochun Lin, Yuanhong Teng, Wancheng Yu, Ya Wang, Changkui Duan, Fazhan Shi - Effective Dynamics for Weakly Interacting Bosons in an Iterated High-Density Thermodynamic Limit - https://arxiv.org/abs/2510.00839 - arXiv:2510.00839v3 Announce Type: replace-cross -Abstract: We study the time evolution of weakly interacting Bose gases on a three-dimensional torus of arbitrary volume. The coupling constant is supposed to be inversely proportional to the density, which is considered to be large and independent of the particle number. We take into account a class of initial states exhibiting quasi-complete Bose-Einstein condensation. For each fixed time in a finite interval, we prove the convergence of the one-particle reduced density matrix towards the projection onto the normalised order parameter describing the condensate - evolving according to the Hartree equation - in the iterated limit where the volume (and therefore the particle number), and subsequently the density go to infinity. The rate of convergence depends only on the density and on the decay of both the expected number of particles and the energy of the initial quasi-vacuum state. - oai:arXiv.org:2510.00839v3 - math-ph - cond-mat.quant-gas - math.MP + Krylov Complexity for Open Quantum System: Dissipation and Decoherence + https://arxiv.org/abs/2509.14810 + arXiv:2509.14810v2 Announce Type: replace-cross +Abstract: We investigate Krylov complexity in open quantum systems using Lindblad master equations for bosonic bath models, with particular emphasis on the Caldeira--Leggett model. Krylov complexity is computed from the moments of the two-point function within the standard master equation framework. For the damped harmonic oscillator, the results reveal clear dissipative features in Krylov complexity. In the Caldeira--Leggett model, in the high-temperature limit, we find that Krylov complexity saturates in the full system and reproduces the expected dissipative behavior when the decoherence term is suppressed in the master equation. Conversely, when the dissipative term is suppressed, the contribution from decoherence exhibits the familiar oscillatory dynamics of the coherent system, along with additional novel features. However, Krylov complexity appears insensitive to the onset of decoherence, as no clear distinctive signature is observed. We attribute this to the fact that Krylov complexity is defined in the Krylov basis, which does not coincide with the conventional basis typically used to study decoherence. + oai:arXiv.org:2509.14810v2 + hep-th quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Daniele Ferretti, Kalle Koskinen + Arpan Bhattacharyya, Sayed Gool, S. Shajidul Haque - Efficient Quantum Simulation of Non-Adiabatic Molecular Dynamics with Precise Electronic Structure - https://arxiv.org/abs/2512.02376 - arXiv:2512.02376v2 Announce Type: replace-cross -Abstract: In the study of non-adiabatic chemical processes such as photocatalysis and photosynthesis, non-adiabatic molecular dynamics (NAMD) is an indispensable theoretical tool, which requires precise potential energy surfaces (PESs) of ground and excited states. Quantum computing offers promising potential for calculating PESs that are intractable for classical computers. However, its realistic application poses significant challenges to the development of quantum algorithms that are sufficiently general to enable efficient and precise PES calculations across chemical systems with diverse properties, as well as to seamlessly adapt existing NAMD theories to quantum computing. In this work, we introduce a quantum-adapted extension to the Landau-Zener-Surface-Hopping (LZSH) NAMD. This extension incorporates curvature-driven hopping corrections that protect the population evolution while maintaining the efficiency gained from avoiding the computation of non-adiabatic couplings (NACs), as well as preserving the trajectory independence that enables parallelization. Furthermore, to ensure the high-precision PESs required for surface hopping dynamics, we develop a sub-microhartree-accurate PES calculation protocol. This protocol supports active space selection, enables parallel acceleration either on quantum or classical clusters, and demonstrates adaptability to diverse chemical systems - including the charged H3+ ion and the C2H4 molecule, a prototypical multi-reference benchmark. This work paves the way for practical application of quantum computing in NAMD, showcasing the potential of parallel simulation on quantum-classical heterogeneous clusters for ab-initio computational chemistry. - oai:arXiv.org:2512.02376v2 - physics.chem-ph + Hadronic scattering in (1+1)D SU(2) lattice gauge theory from tensor networks + https://arxiv.org/abs/2511.00154 + arXiv:2511.00154v2 Announce Type: replace-cross +Abstract: We present a first real-time study of hadronic scattering in a (1+1)-dimensional SU(2) lattice gauge theory with fundamental fermions using tensor-network techniques. Working in the gaugeless Hamiltonian formulation -- where the gauge field is exactly integrated out and no truncation of the electric flux is required -- we investigate scattering processes across sectors of fixed global baryon number $B = 0, 1, 2$. These correspond respectively to meson-meson, meson-baryon, and baryon-baryon collisions. At strong coupling, the $B = 0$ and $B = 2$ channels exhibit predominantly elastic dynamics closely resembling those of the U(1) Schwinger model. In contrast, the mixed $B = 1$ sector shows qualitatively new behavior: meson and baryon wave packets become entangled during the collision, and depending on their initial kinematics, the slower state becomes spatially delocalized while the faster one propagates ballistically. We characterize these processes through local observables, entanglement entropy, and the information-lattice, which together reveal how correlations build up and relax during the interaction. Our results establish a first benchmark for non-Abelian real-time scattering from first principles and open the path toward quantum-simulation studies of baryon-number dynamics and inelastic processes in gauge theories. + oai:arXiv.org:2511.00154v2 + hep-lat + hep-ph + nucl-th quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by-nc-nd/4.0/ - Tianyi Li, Yumeng Zeng, Qiming Ding, Zixuan Huo, Xiaosi Xu, Jiajun Ren, Diandong Tang, Xiaoxia Cai, Xiao Yuan + Jo\~ao Barata, Juan Hormaza, Zhong-Bo Kang, Wenyang Qian - The swap transpose on couplings translates to Petz' recovery map on quantum channels - https://arxiv.org/abs/2512.04919 - arXiv:2512.04919v2 Announce Type: replace-cross -Abstract: In [Ann. Henri Poincar\'e, {\bf 22} (2021), 3199-3234], De Palma and Trevisan described a one-to-one correspondence between quantum couplings and quantum channels realizing transport between states. The aim of this short note is to demonstrate that taking the Petz recovery map for a given channel and initial state is precisely the counterpart of the swap transpose operation on couplings. That is, the swap transpose of the coupling $\Pi_{\Phi}$ corresponding to the channel $\Phi$ and initial state $\rho$ is the coupling $\Pi_{rec}$ corresponding to the Petz recovery map $\Phi_{rec}.$ - oai:arXiv.org:2512.04919v2 + Variational Method in Quantum Field Theory + https://arxiv.org/abs/2511.08686 + arXiv:2511.08686v2 Announce Type: replace-cross +Abstract: We develop a variational framework for addressing two-dimensional non-integrable quantum field theories through the exact structure of their integrable counterparts. Concentrating on the $\varphi^4$ Landau-Ginzburg model, we use the analytical Vacuum Expectation Values and Form Factors of local operators in the sinh-Gordon theory as the foundation of a variational ansatz. In this way, we obtain controlled estimates of central physical quantities of the $\varphi^4$ theory - such as the finite-volume ground-state energy and the physical mass as a function of the coupling constant. The strengths of the variational methods are leveraged in combination with the Hamiltonian truncation techniques and the LeClair-Mussardo formula, which also allow to probe the accuracy of the variational approximation varying the system size. Within the weak-coupling regime, a detailed numerical analysis reveals the behaviour of the finite-volume spectrum, the ground-state energy, and the elastic part of the scattering matrix, showing how the rigorous machinery of integrable models can serve as a guiding light into the complex landscape of non-integrable quantum field dynamics. + oai:arXiv.org:2511.08686v2 + hep-th + cond-mat.stat-mech + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + Arthur Hutsalyuk, M\'arton L\'ajer, Giuseppe Mussardo, Andrea Stampiggi + + + Vacuum Energy and Topological Mass in Interacting Elko and Scalar Field Theories + https://arxiv.org/abs/2512.08750 + arXiv:2512.08750v3 Announce Type: replace-cross +Abstract: In this paper, we consider a four-dimensional system composed of a mass-dimension-one fermionic field, also known as Elko, interacting with a real scalar field. Our main objective is to analyze the Casimir effects associated with this system, assuming that both the Elko and scalar fields satisfy Dirichlet boundary conditions on two large parallel plates separated by a distance $L$. In this scenario, we calculate the vacuum energy density and its first-order correction in the coupling constants of the theory. Additionally, we consider the mass correction for each field separately, namely the topological mass that arises from the boundary conditions imposed on the fields and which also depends on the coupling constants. To develop this analysis, we use the mathematical formalism known as the effective potential, expressed as a path integral in quantum field theory. + oai:arXiv.org:2512.08750v3 + hep-th math-ph math.MP - math.OA quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Gergely Bunth, J\'ozsef Pitrik, Tam\'as Titkos, D\'aniel Virosztek + http://creativecommons.org/licenses/by/4.0/ + A. J. D. Farias Junior, A. Smirnov, Herondy F. Santana Mota, E. R. Bezerra de Mello - Programmable Assembly of Ground State Fermionic Tweezer Arrays - https://arxiv.org/abs/2512.09849 - arXiv:2512.09849v2 Announce Type: replace-cross -Abstract: We demonstrate deterministic preparation of arbitrary two-component product states of fermionic $^6$Li atoms in an 8$\times$8 optical tweezer array, achieving motional ground-state fidelities above $98.5\,\%$. Leveraging the large differential magnetic moments for spin-resolution, with parallelized site- and number-resolved control, our approach addresses key challenges for low-entropy quantum state engineering. Combined with high-fidelity spin-, site-, and density-resolved readout within a single $20\,\mathrm{\mu s}$ exposure, and $3\,\mathrm{s}$ experimental cycles, these advances establish a fast, scalable, and programmable architecture for fermionic quantum simulation. - oai:arXiv.org:2512.09849v2 - cond-mat.quant-gas - physics.atom-ph + A sine-square deformation approach to quantum critical points in one-dimensional systems + https://arxiv.org/abs/2512.14149 + arXiv:2512.14149v2 Announce Type: replace-cross +Abstract: We propose a method to determine the quantum phase boundaries of one-dimensional systems using sine-square deformation (SSD). Based on the proposition, supported by several exactly solved cases though not proven in full generality, that "if a one-dimensional system is gapless, then the expectation value of any local observable in the ground state of the Hamiltonian with SSD exhibits translational symmetry in the thermodynamic limit," we determine the quantum critical point as the location where a local observable becomes site-independent, identified through finite-size scaling analysis. As case studies, we consider two models: the antiferromagnetic Ising chain in mixed transverse and longitudinal magnetic fields with nearest-neighbor and long-range interactions. We calculate the ground state of these Hamiltonians with SSD using the density-matrix renormalization-group algorithm and evaluate the local transverse magnetization. For the nearest-neighbor model, we show that the quantum critical point can be accurately estimated by our procedure with systems of up to 84 sites, or even smaller, in good agreement with results from the literature. For the long-range model, we find that the phase boundary between the antiferromagnetic and paramagnetic phases is slightly shifted relative to the nearest-neighbor case, leading to a reduced region of antiferromagnetic order. Moreover, we propose an experimental procedure to implement the antiferromagnetic $J_1$-$J_2$ Ising couplings with SSD using Rydberg atom arrays in optical tweezers, which can be achieved within a very good approximation. Because multiple independent scaling conditions naturally emerge, our approach enables precise determination of quantum critical points and possibly even the extraction of additional critical phenomena, such as critical exponents, from relatively small system sizes. + oai:arXiv.org:2512.14149v2 + cond-mat.str-el quant-ph - Fri, 12 Dec 2025 00:00:00 -0500 + Fri, 19 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Naman Jain, Jin Zhang, Marcus Culemann, Philipp M. Preiss + Yuki Miyazaki, Shiori Tanigawa, Giacomo Marmorini, Nobuo Furukawa, Daisuke Yamamoto + + + Characterising the sets of quantum states with non-negative Wigner function + https://arxiv.org/abs/2512.14820 + arXiv:2512.14820v2 Announce Type: replace-cross +Abstract: For Hilbert spaces $\mathcal H\subseteq L^2(\mathbb R)$ we consider the convex sets $\mathcal D_+(\mathcal H)$ of Wigner-positive states (WPS), i.e.~density matrices over $\mathcal H$ with non-negative Wigner function. We investigate the topological structure of these sets, namely concerning closure, compactness, interior and boundary (in a relative topology induced by the trace norm). We also study their geometric structure and construct minimal sets of states that generate $\mathcal D_+(\mathcal H)$ through convex combinations. If $\mathcal H$ is finite-dimensional, the existence of such sets follows from a central result in convex analysis, namely the Krein-Milman theorem. In the infinite-dimensional case $\mathcal H=L^2(\mathbb R)$ this is not so, due to lack of compactness of the set $\mathcal D_+(\mathcal H)$. Nevertheless, we prove that a Krein-Milman theorem holds in this case, which allows us to extend most of the results concerning the sets of generators to the infinite-dimensional setting. Finally, we study the relation between the finite and infinite-dimensional sets of WPS, and prove that the former provide a hierarchy of closed subsets, which are also proper faces of the latter. These results provide a basis for an operational characterisation of the extreme points of the sets of WPS, which we undertake in a companion paper. Our work offers a unified perspective on the topological and geometric properties of the sets of WPS in finite and infinite dimensions, along with explicit constructions of minimal sets of generators. + oai:arXiv.org:2512.14820v2 + math-ph + math.MP + quant-ph + Fri, 19 Dec 2025 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Nicolas J. Cerf, Ulysse Chabaud, Jack Davis, Nuno C. Dias, Jo\~ao N. Prata, Zacharie Van Herstraeten