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" @@ -7,1440 +7,1582 @@ http://www.rssboard.org/rss-specification en-us - Thu, 11 Dec 2025 05:00:00 +0000 + Fri, 12 Dec 2025 05:00:05 +0000 rss-help@arxiv.org - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 Saturday Sunday - An ETH-ansatz-based environmental-branch approach to master equation - https://arxiv.org/abs/2512.09007 - arXiv:2512.09007v1 Announce Type: new -Abstract: In this paper, a method for deriving master equation is developed for a generic small quantum system, which is locally coupled to an environment as a many-body quantum chaotic system that satisfies the eigenstate thermalization hypothesis ansatz, resorting to neither the Born approximation nor the Markov approximation. The total system undergoes Schr\"{o}dinger evolution, under an initial condition in which the environmental branches possess no correlation with the interaction Hamiltonian. Derivation of the master equation is based on piecewise usage of a second-order expansion of a formal expression, which is derived for the evolution of the environmental branches. Approximations used in the derivation are mainly based on dynamic properties of the environment. - oai:arXiv.org:2512.09007v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.dis-nn + cond-mat.stat-mech + hep-th + nlin.CD + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Wen-ge Wang + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Naga Dileep Varikuti, Soumik Bandyopadhyay, Philipp Hauke - The Richness of Bell Nonlocality: Generalized Bell Polygamy and Hyper-Polygamy - https://arxiv.org/abs/2512.09034 - arXiv:2512.09034v1 Announce Type: new -Abstract: Non-classical quantum correlations underpin both the foundations of quantum mechanics and modern quantum technologies. Among them, Bell nonlocality is a central example. For bipartite Bell inequalities, nonlocal correlations obey strict monogamy: a violation of one inequality precludes violations of other inequalities on the overlapping subsystems. In the multipartite setting, however, Bell nonlocality becomes inherently polygamous. This was previously shown for subsystems obtained by removing a single particle from an $N$-partite system. Here, we generalize this result to arbitrary $(N-k)$-partite subsystems with $k>0$. We demonstrate that a single $N$-qubit state can violate all $\binom{N}{k}$ relevant Bell inequalities simultaneously. We further construct an $N$-qubit Bell inequality, obtained by symmetrizing the $(N-k)$-qubit ones, that is maximally violated by states exhibiting this generalized polygamy. We compare these violations with those achievable by GHZ states and show that polygamy offers an advantage in multipartite scenarios, providing new insights into scalable certification of non-classicality in quantum devices. Our analysis relies on symmetry properties of the MABK inequalities. Finally, we show that this behavior can occur across multiple subsystem sizes, a phenomenon we call hyper-polygamy. These structures reveal the remarkable abundance of nonlocality present in multipartite quantum states and offer perspectives for their applications in quantum technologies. - oai:arXiv.org:2512.09034v1 + 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 - Thu, 11 Dec 2025 00:00:00 -0500 + math-ph + math.MP + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Gerard Angl\`es Munn\'e, Pawe{\l} Cie\'sli\'nski, Jan W\'ojcik, Wies{\l}aw Laskowski + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Farid Shahandeh, Theodoros Yianni, Mina Doosti - Slow dynamics and magnon bound states in the 2D long-range quantum Ising model - https://arxiv.org/abs/2512.09037 - arXiv:2512.09037v1 Announce Type: new -Abstract: The dynamics of long-range quantum Ising models represents a current frontier in experimental physics, notably in trapped ions or Rydberg atomic systems. However, a theoretical description of these dynamics beyond 1D remains a significant challenge for conventional methods. Here, we address this challenge by means of neural quantum states to simulate global quenches from the fully polarized ferromagnetic state in the 2D quantum Ising model with power-law decaying interactions. From these numerically exact simulations, we find that the dynamics exhibit slow relaxation with long-lived oscillations. We explain this behavior through a theory for the formation of magnon bound states, which are generated, as we show, through effective attractive interactions between magnons that persist over several lattice sites due to the power-law nature of the interactions. Our results are readily observable in current quantum simulation platforms realizing long-range interacting models such as in Rydberg atomic systems. - oai:arXiv.org:2512.09037v1 + 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 quant-ph - cond-mat.stat-mech - Thu, 11 Dec 2025 00:00:00 -0500 + physics.app-ph + physics.optics + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Vighnesh Dattatraya Naik, Markus Heyl + Helaman Flores, Mahmoud Jalali Mehrabad, Siavash Mirzaei-Ghormish, Ryan M. Camacho, Dirk Englund - Optimizing the dynamical preparation of quantum spin lakes on the ruby lattice - https://arxiv.org/abs/2512.09040 - arXiv:2512.09040v1 Announce Type: new -Abstract: Quantum spin liquids are elusive long-range entangled states. Motivated by experiments in Rydberg quantum simulators, recent excitement has centered on the possibility of dynamically preparing a state with quantum spin liquid correlation even when the ground state phase diagram does not exhibit such a topological phase. Understanding the microscopic nature of such quantum spin "lake" states and their relationship to equilibrium spin liquid order remains an essential question. Here, we extend the use of approximately symmetric neural quantum states for real-time evolution and directly simulate the dynamical preparation in systems of up to $N=384$ atoms. We analyze a variety of spin liquid diagnostics as a function of the preparation protocol and optimize the extent of the quantum spin lake thus obtained. In the optimal case, the prepared state shows spin-liquid properties extending over half the system size, with a topological entanglement entropy plateauing close to $\gamma = \ln 2$. We extract two physical length scales $\lambda$ and $\xi$ which constrain the extent of the quantum spin lake $\ell$ from above and below. - oai:arXiv.org:2512.09040v1 + 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 quant-ph - cond-mat.dis-nn - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - DinhDuy Vu, Dominik S. Kufel, Jack Kemp, Lode Pollet, Chris R. Laumann, Norman Y. Yao + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Ravi Kunjwal - Quantum bootstrap for central potentials - https://arxiv.org/abs/2512.09041 - arXiv:2512.09041v1 Announce Type: new -Abstract: We study the quantum-mechanical bootstrap as it applies to the bound states of several central potentials in three dimensions. As part of this effort, we show how the bootstrap approach may be applied to ``non-algebraic'' potentials, such as the Yukawa potential (which asymptotically decays as an exponential) and a Gaussian potential. We additionally review the bootstrap of the Coulomb potential, demonstrate a high-precision bootstrap of the Cornell potential, and study conformal quantum mechanics. These results further recommend the bootstrap as a numerical method for high-precision calculations of ground-state physics, where applicable: for example, we are able to determine the critical coupling in the Cornell potential to better than one part in $10^7$, the most precise determination to date. Lower bounds on energies are also of high precision, occasionally one part in greater than $10^8$. Finally, we discuss the circumstances under which we are able to obtain meaningful upper bounds on ground-state energies. - oai:arXiv.org:2512.09041v1 + 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 quant-ph - hep-lat - hep-th - Thu, 11 Dec 2025 00:00:00 -0500 + math.OC + Fri, 12 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Oleg V. Morzhin + + + 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 + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Scott Lawrence, Brian McPeak + Siavash Mirzaei-Ghormish, Mahmoud Jalali Mehrabad, Helaman Flores, Dirk Englund, Ryan M. Camacho - Dressed-state Hamiltonian engineering in a strongly interacting solid-state spin ensemble - https://arxiv.org/abs/2512.09043 - arXiv:2512.09043v1 Announce Type: new -Abstract: In quantum science applications, ranging from many-body physics to quantum metrology, dipolar interactions in spin ensembles are controlled via Floquet engineering. However, this technique typically reduces the interaction strength between spins, and effectively weakens the coupling to a target sensing field, limiting the metrological sensitivity. In this work, we develop and demonstrate a method for direct tuning of the native interaction in an ensemble of nitrogen-vacancy (NV) centers in diamond. Our approach utilizes dressed-state qubit encoding under a magnetic field perpendicular to the crystal lattice orientation. This method leads to a $3.2\times$ enhancement of the dimensionless coherence parameter $JT_2$ compared to state-of-the-art Floquet engineering, and a $2.6\times$ ($8.3~$dB) enhanced sensitivity in AC magnetometry. Utilizing the extended coherence we experimentally probe spin transport at intermediate to late times. Our results provide a powerful Hamiltonian engineering tool for future studies with NV ensembles and other interacting higher-spin ($S>\frac{1}{2}$) systems. - oai:arXiv.org:2512.09043v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.quant-gas + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Haoyang Gao, Nathaniel T. Leitao, Siddharth Dandavate, Lillian B. Hughes Wyatt, Piotr Put, Mathew Mammen, Leigh S. Martin, Hongkun Park, Ania C. Bleszynski Jayich, Mikhail D. Lukin + Chun Hei Leung, Pak-Tik Fong, Tianyi Yan, Weibin Li - Subradiant collective states for precision sensing via transmission spectra - https://arxiv.org/abs/2512.09050 - arXiv:2512.09050v1 Announce Type: new -Abstract: When an ensemble of quantum emitters interacts with a common radiation field, their emission becomes collective, giving rise to superradiant and subradiant states, characterized by broadened and narrowed linewidths. In this work, we propose to harness subradiant states for quantum metrology; such states naturally arise in subwavelength-spaced atomic arrays in free space and in small ensembles of emitters coupled to one-dimensional waveguides. We demonstrate that their collective optical response yields sharp, narrow features in the transmittance spectrum, which can be used to enhance sensitivity to external perturbations. This improved sensitivity can be applied to atomic clock operation, spatially resolved imaging of emitter positions, and enables precise detection of both global and spatially varying detunings (such as those induced by electromagnetic fields or gravitational gradients). - oai:arXiv.org:2512.09050v1 + 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 quant-ph - physics.atom-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Diego Zafra-Bono, Oriol Rubies-Bigorda, Susanne F. Yelin + Newshaw Bahreyni, Paul M. Alsing, Carlo Cafaro, Walid Redjem, Christian Corda - Quantum Clocks Tick Faster: Entanglement, Contextuality, and the Flow of Time - https://arxiv.org/abs/2512.09100 - arXiv:2512.09100v1 Announce Type: new -Abstract: Building on the recent proposal that a single ``bona fide'' clock suffices to define spacetime's metric, we introduce an Entangled Clock protocol based on singlet-state correlations. Invoking Zeilinger's Foundational Principle, we argue that while the local flow of time, operationally defined as a sequence of detector ``ticks,'' is irreducibly random (one bit per elementary system), the synchronized flow between spatially separated observers depends on their measurement geometry. Comparing the quantum prediction for the coincidence rate with Peres' classical ``bomb fragment'' model, we find that at obtuse relative angles the entangled clock exhibits a 13 percent higher synchronized tick rate than this linear classical benchmark. This ``temporal acceleration'' is linked to contextuality: following Peres, ``unperformed experiments have no results,'' and quantum systems are not constrained to maintain consistency with all counterfactual measurement settings. We stress, however, that for any single measurement angle a suitably tailored classical model can reproduce the quantum rate. The genuinely nonclassical character of the entangled clock emerges only when correlations at several angles are considered simultaneously and are shown to violate Bell-type inequalities. In this sense, the violation of Bell-type bounds serves as a certification that the shared time standard is genuinely quantum. - oai:arXiv.org:2512.09100v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Karl Svozil + 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 - Islands of Instability in Nonlinear Wavefunction Models in the Continuum: A Different Route to "Chaos" - https://arxiv.org/abs/2512.09109 - arXiv:2512.09109v1 Announce Type: new -Abstract: In two previous papers the author described ``Islands of Instability" that may appear in wavefunction models with nonlinear evolution (of a type proposed originally in the context of the Measurement Problem). Such ``IsoI" represent a new scenario for Hamiltonian systems implying so-called ``chaos". Criteria was derived for, and shown to be fulfilled in, some finite-dimensional (multi-qubit) models, and generalized in the second paper to continuum models. But the only example produced of the latter was a model whose linear Schrodinger equation was exactly-solvable. As exact solutions of many-body problems are rare, here I show that the instability criteria can be verified by plugging test-functions into certain computable expressions, bypassing the solvability blockade. The method can accommodate realistic inter-molecular potentials and so may be relevant to instabilities in fluids and gasses. - oai:arXiv.org:2512.09109v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + eess.SP + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - W. David Wick + 10.1109/MNET.2025.3643793 + Phuc V. Trinh, Shinya Sugiura, Carlo Ottaviani, Chao Xu, Lajos Hanzo - Enhanced Squeezing and Faster Metrology from Layered Quantum Neural Networks - https://arxiv.org/abs/2512.09137 - arXiv:2512.09137v1 Announce Type: new -Abstract: Spin squeezing is a powerful resource for quantum metrology, and recent hardware platforms based on interacting qubits provide multiple possible architectures to generate and reverse squeezing during a sensing protocol. In this work, we compare the sensing performance of three such architectures: quantum reservoir computers (QRCs), quantum perceptrons, and multi-layer quantum neural networks (QNNs), when used as squeezing-based field sensors. For all models, we consider a standard metrological sequence consisting of coherent-spin preparation, one-axis-twisting dynamics, field encoding via a weak rotation, time-reversal, and collective readout. We show that a single quantum perceptron generates the same optimal sensitivity as a QRC, but in the perturbative regime it benefits from accelerated squeezing due to steering by the output qubit. Stacking perceptrons into a QNN further amplifies this effect: in a 2-layer QNN with N_in input and N_out output qubits, the optimal squeezing time is reduced by a factor of N_out, while the achievable phase sensitivity remains Heisenberg-limited, Delta phi ~ 1/(N_in + N_out). Moreover, if the layers are used sequentially, first using the outputs to squeeze the inputs and then the inputs to squeeze the outputs, the two contributions to the response add constructively. This yields a sqrt(2) enhancement in sensitivity over a QRC when N_in = N_out and requires shorter total squeezing time. Generalizing to L layers, we show that the metrological gain scales as sqrt(L) while the required squeezing time decreases as 1/N_l, where N_l is the number of qubits per layer. Our results demonstrate that the structure of quantum neural networks can be exploited not only for computation, but also to engineer faster and more sensitive squeezing-based quantum sensors. - oai:arXiv.org:2512.09137v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + eess.SP + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Nickholas Gutierrez, Rodrigo Araiza Bravo, Susanne Yelin + 10.1109/MCOM.003.2300835 + IEEE Communications Magazine, vol. 62, no. 10, pp. 62-68, Oct. 2024 + Phuc V. Trinh, Shinya Sugiura - Transition rates and their applications in accelerated single-qubit for fermionic spinor field coupling - https://arxiv.org/abs/2512.09144 - arXiv:2512.09144v1 Announce Type: new -Abstract: In this work, we investigate the interaction between a uniformly accelerated single qubit and a fermionic spinor field. Here we consider both the massless and the massive fermionic spinor fields. The qubit-field interaction occurs over a finite time and was evolved via perturbation theory. This approach yields the transition probability rates, from which we subsequently evaluate the quantum coherence of an Unruh-DeWitt (UDW) detector initially prepared in a qubit state. Our findings reveal that the UDW detector responds more when coupled with the fermionic field, and consequently, quantum coherence (for the fermionic case) degrades much more rapidly when compared to the case of the qubit linearly coupled with the scalar field. Moreover, the analysis suggests that particle mass plays a protective role against Unruh-induced decoherence as the rest mass energy becomes comparable to the detector's energy-level spacing, the detector's excitation probability and response decreases, which leads to the mitigation of quantum coherence degradation in accelerated quantum systems. - oai:arXiv.org:2512.09144v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Arnab Mukherjee, Sunandan Gangopadhyay, P. H. M. Barros, H. A. S. Costa + 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 - Exact and Efficient Stabilizer Simulation of Thermal-Relaxation Noise for Quantum Error Correction - https://arxiv.org/abs/2512.09189 - arXiv:2512.09189v1 Announce Type: new -Abstract: Stabilizer-based simulation of quantum error-correcting codes typically relies on the Pauli-twirling approximation (PTA) to render non-Clifford noise classically tractable, but PTA can distort the behavior of physically relevant channels such as thermal relaxation. Physically accurate noise simulation is needed to train decoders and understand the noise suppression capabilities of quantum error correction codes. In this work, we develop an exact and stabilizer-compatible model of qubit thermal relaxation noise and show that the combined amplitude damping and dephasing channel admits a fully positive probability decomposition into Clifford operations and reset whenever $T_2 \leqslant T_1$. For $T_2 > T_1$, the resulting decomposition is negative, but allows a smaller sampling overhead versus independent channels. We further introduce an approximated error channel with reset that removes the negativity of the decomposition while achieving higher channel fidelity to the true thermal relaxation than PTA, and extend our construction to finite temperature relaxation. We apply the exact combined model to investigate large surface codes and bivariate bicycle codes on superconducting platforms with realistic thermal relaxation error. The differing logical performances across code states further indicate that noise-model-informed decoders will be essential for accurately capturing thermal-noise structure in future fault-tolerant architectures. - oai:arXiv.org:2512.09189v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Sean R. Garner, Nathan M. Myers, Meng Wang, Samuel Stein, Chenxu Liu, Ang Li + 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 - Parallel accelerated electron paramagnetic resonance spectroscopy using diamond sensors - https://arxiv.org/abs/2512.09230 - arXiv:2512.09230v1 Announce Type: new -Abstract: The nitrogen-vacancy (NV) center can serve as a magnetic sensor for electron paramagnetic resonance (EPR) measurements. Benefiting from its atomic size, the diamond chip can integrate a tremendous amount of NV centers to improve the magnetic-field sensitivity. However, EPR spectroscopy using NV ensembles is less efficient due to inhomogeneities in both sensors and targets. Spectral line broadening induced by ensemble averaging is even detrimental to spectroscopy. Here we show a kind of cross-relaxation EPR spectroscopy at zero field, where the sensor is tuned by an amplitude-modulated control field to match the target. The modulation makes detection robust to the sensor's inhomogeneity, while zero-field EPR is naturally robust to the target's inhomogeneity. We demonstrate an efficient EPR measurement on an ensemble of roughly 30000 NV centers. Our method shows the ability to not only acquire unambiguous EPR spectra of free radicals, but also monitor their spectroscopic dynamics in real time. - oai:arXiv.org:2512.09230v1 + 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 quant-ph - physics.bio-ph - physics.chem-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cs.CC + cs.DS + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/PhysRevLett.134.130801 - Phys. Rev. Lett. 134, 130801 (2025) - Zhehua Huang, Zhengze Zhao, Fei Kong, Zhecheng Wang, Pengju Zhao, Xiangtian Gong, Xiangyu Ye, Ya Wang, Fazhan Shi, Jiangfeng Du + Antonio Anna Mele, Lennart Bittel - Spontaneous Decoherence from Imaginary-Order Spectral Deformations - https://arxiv.org/abs/2512.09236 - arXiv:2512.09236v1 Announce Type: new -Abstract: We examine a mechanism of spontaneous decoherence in which the generator of quantum dynamics is replaced by the imaginary-order spectral deformation $H^{1+i\beta}$ of a positive 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 showing that oscillatory contributions to amplitudes or decoherence functionals decay at least as $O(1/|\beta|)$. The Born rule and the Hilbert-space inner product remain unchanged; the modification is entirely dynamical. - The physical motivation for the deformation arises from clock imperfections, renormalization-group and effective-action corrections that introduce logarithmic spectral terms, and semiclassical quantum-gravity analyses in which complex actions produce spectral factors of the form $E^{i\beta}$. Examples including FRW minisuperspace, quartic potentials, curved-background Hamiltonians, and a Schwarzschild interior-type model illustrate how the mechanism yields explicit decoherence rates. The parameter $\beta$ may be experimentally constrained through precision coherence measurements in low-noise quantum platforms. The mechanism contrasts with Milburn-type intrinsic decoherence, Diosi-Penrose gravitational collapse, and real-order fractional dynamics in that it acts purely through deterministic spectral phases of a single Hamiltonian. The analysis positions the framework as a compact and testable phenomenological representation of logarithmic spectral corrections appearing in quantum-gravity-motivated effective theories. - oai:arXiv.org:2512.09236v1 + 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 quant-ph - gr-qc - hep-th - math-ph - math.MP - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 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 + + + 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 + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sridhar Tayur + Ananga Mohan Datta, William J. Munro, Nicolo Lo Piparo, Kae Nemoto - Harvesting entanglement from the Lorentz-violating quantum field vacuum in a dipolar Bose-Einstein condensate - https://arxiv.org/abs/2512.09263 - arXiv:2512.09263v1 Announce Type: new -Abstract: We theoretically propose an experimentally viable scheme to explore the transfer of nonclassical correlations from a dipolar Bose-Einstein condensate (BEC) to a pair of impurities immersed in it. Operating at ultra-low temperature, density fluctuations of the dipolar BEC emulate a vacuum field with Lorentz-violating dispersion, while the two impurities function as Unruh-DeWitt detectors for the BEC quasiparticles. We study the harvesting of entanglement from the quantum vacuum of this analogue Lorentz-violating quantum field by spatially separated Unruh-DeWitt detectors. Our analysis reveals key parameter dependencies that optimize the harvesting of entanglement. In particular, unlike the Lorentz-invariant case, smoother detector switchings does not enhance the entanglement harvesting efficiency from the Lorentz-violating quantum field vacuum. Moreover, the strength of the Lorentz-invariant violation can shift the optimal energy structure of the detectors for harvesting entanglement from the Lorentz-violating quantum field vacuum-a clear deviation from the Lorentz-invariant scenario. As a fundamental quantum mechanical setup, our quantum fluid platform provides an experimentally realizable testbed for examining the entanglement harvesting protocol from an effective Lorentz-violating quantum field vacuum using a pair of impurity probers, which may also has potential implications for exploring the Lorentz-invariant violation in quantum field theory. - oai:arXiv.org:2512.09263v1 + 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 quant-ph - gr-qc - hep-th - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zehua Tian, Weiping Yao, Xiaobao Liu, Mengjie Wang, Jieci Wang, Jiliang Jing + http://creativecommons.org/licenses/by/4.0/ + Chi-Fang Chen, Robbie King - Mpemba as an Emergent Effect of System Relaxation - https://arxiv.org/abs/2512.09324 - arXiv:2512.09324v1 Announce Type: new -Abstract: The Mpemba effect (MpE), where a far-from-equilibrium state of a system relaxes faster compared to a state closer to it, is a well-known counterintuitive phenomenon in classical and quantum systems. Various system-specific theories have been proposed to explain this anomalous behavior in driven systems, though the fundamental mechanism of MpE in undriven systems, where MpE was first observed, remains unresolved. This paper provides a generic model of MpE for a quantum system following Markovian relaxation dynamics, regardless of system structure or environment. The key lies in the overlap of initial states with the fast relaxation mode; here, the constituents create a fast decay mode via interaction through the shared environment to show MpE, indicating MpE happens due to the collective behavior of the system. I also show that a system with anisotropic relaxation naturally exhibits MpE, even without a shared environment among the particles. - oai:arXiv.org:2512.09324v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + physics.bio-ph + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Gourab Das + 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 - Routes of Transport in the Path Integral Lindblad Dynamics through State-to-State Analysis - https://arxiv.org/abs/2512.09362 - arXiv:2512.09362v1 Announce Type: new -Abstract: Analyzing routes of transport for open quantum systems with non-equilibrium initial conditions is extremely challenging. The state-to-state approach [A. Bose, and P.L. Walters, J. Chem. Theory Comput. 2023, 19, 15, 4828-4836] has proven to be a useful method for understanding transport mechanisms in quantum systems interacting with dissipative thermal baths, and has been recently extended to non-Hermitian systems to account for empirical loss. These non-Hermitian descriptions are, however, not capable of describing empirical processes of more general nature, including but not limited to a variety of pumping processes. We extend the state-to-state analysis to account for Lindbladian descriptions of generic dissipative, pumping and decohering processes acting on a system which is exchanging energy with a thermal bath. This Lindblad state-to-state method can elucidate routes of transport in systems coupled to a bath and additionally acted upon by Lindblad jump operators. The method is demonstrated using examples of excitonic aggregates subject to incoherent pumping and draining processes. Using this new state-to-state formalism, we demonstrate the establishment of steady-state excitonic currents across molecular aggregates, yielding a different first-principles approach to quantifying the same. - oai:arXiv.org:2512.09362v1 + 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 quant-ph - physics.chem-ph - Thu, 11 Dec 2025 00:00:00 -0500 + physics.bio-ph + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Devansh Sharma, Amartya Bose + Yu Chen, Qi Zhang, Yuanhong Teng, Chihang Luo, Zhijie Li, Jinpeng Liu, Ya Wang, Fazhan Shi, Jiangfeng Du - Compact and efficient quantum frequency conversion of a fiber-pigtailed single-photon source - https://arxiv.org/abs/2512.09390 - arXiv:2512.09390v1 Announce Type: new -Abstract: Quantum frequency converters are key enabling technologies in photonic quantum information science to bridge the gap between quantum emitters and telecom photons. Here, we report a co- herent frequency converter scheme combining a fiber-coupled nonlinear optical Lithium Niobate waveguide with a fiber-pigtailed single-photon source based on semiconductor quantum dots. Single and indistinguishable photons are converted from 925.7 nm to the telecommunication C-band, with a 48.4% end-to-end efficiency and full preservation of single-photon purity and indistinguishability. The integration of the two fiber-based modules achieving top-level performance represents an im- portant step toward the practical interconnection of future quantum information processing systems operating at different wavelengths. - oai:arXiv.org:2512.09390v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + math.OC + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Mathis Cohen, Anthony Martin, Romain Dalidet, Florian Pastier, Marie Billard, Aristide Lemaitre, Val\'erian Giesz, Niccolo Somaschi, Sarah Thomas, Pascale Senellart-Mardon, S\'ebastien Tanzilli, Laurent Labont\'e + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Oleg V. Morzhin - Two-Photon Bandwidth of Hyper-Entangled Photons in Complex Media - https://arxiv.org/abs/2512.09456 - arXiv:2512.09456v1 Announce Type: new -Abstract: When light propagates through complex media, its output spatial distribution is highly sensitive to its wavelength. This fundamentally limits the bandwidth of applications ranging from imaging to communication. Here, we demonstrate analytically and numerically that the spatial correlations of hyper-entangled photon pairs, simultaneously entangled spatially and spectrally, remain stable across a broad bandwidth: The chromatic modal dispersion experienced by one photon is canceled to first order by its spectrally anti-correlated twin, defining a "two-photon bandwidth" that can far exceed its classical counterpart. We illustrate this modal dispersion cancellation in multimode fibers, thin diffusers and blazed gratings, and demonstrate its utility for broadband wavefront shaping of quantum states. These findings advance our fundamental understanding of quantum light in complex media with applications in quantum imaging, communication, and sensing. - oai:arXiv.org:2512.09456v1 + 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 quant-ph - physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.quant-gas + physics.atom-ph + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Ronen Shekel, Ohad Lib, S\'ebastien M. Popoff, Yaron Bromberg + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Xu Feng, Shuo Liu, Shu Chen, Shi-Xin Zhang - LiePrune: Lie Group and Quantum Geometric Dual Representation for One-Shot Structured Pruning of Quantum Neural Networks - https://arxiv.org/abs/2512.09469 - arXiv:2512.09469v1 Announce Type: new -Abstract: Quantum neural networks (QNNs) and parameterized quantum circuits (PQCs) are key building blocks for near-term quantum machine learning. However, their scalability is constrained by excessive parameters, barren plateaus, and hardware limitations. We propose LiePrune, the first mathematically grounded one-shot structured pruning framework for QNNs that leverages Lie group structure and quantum geometric information. Each gate is jointly represented in a Lie group--Lie algebra dual space and a quantum geometric feature space, enabling principled redundancy detection and aggressive compression. Experiments on quantum classification (MNIST, FashionMNIST), quantum generative modeling (Bars-and-Stripes), and quantum chemistry (LiH VQE) show that LiePrune achieves over $10\times$ compression with negligible or even improved task performance, while providing provable guarantees on redundancy detection, functional approximation, and computational complexity. - oai:arXiv.org:2512.09469v1 + 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 quant-ph - cs.CV - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Haijian Shao, Bowen Yang, Wei Liu, Xing Deng, Yingtao Jiang + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Dong An, Xi Guo - Can Intense Quantum Light Beat Classical Uncertainty Relations? - https://arxiv.org/abs/2512.09558 - arXiv:2512.09558v1 Announce Type: new -Abstract: Uncertainty relations are fundamental to quantum mechanics, encoding limits on the simultaneous measurement of conjugate observables. Violations of joint uncertainty bounds can certify entanglement -- a resource critical for quantum information protocols and increasingly relevant in strong-field physics. Here, we investigate the pairwise time-delay and frequency-bandwidth uncertainties for arbitrary multimode quantum states of light, deriving a general lower bound for their joint product. We find that the nonclassical correction scales inversely with the average photon number, a behavior rooted in the so-called ``monogamy of entanglement''. These results clarify the intensity scaling of quantum advantages in nonclassical light states and highlight the interplay between entanglement and photon statistics. - oai:arXiv.org:2512.09558v1 + 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 quant-ph + cond-mat.mes-hall + physics.app-ph physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Felipe Reibnitz Willemann, Mauro Antezza, Johannes Feist + Zi-Xu Lu, Huai-Bing Zhu, Xuan Zuo, Jie Li - Exceptional points of arbitrary high orders induced by non-Markovian dynamics - https://arxiv.org/abs/2512.09582 - arXiv:2512.09582v1 Announce Type: new -Abstract: Exceptional points are singularities in the spectrum of non-Hermitian systems in which several eigenvectors are linearly dependent and their eigenvalues are equal to each other. Usually it is assumed that the order of the exceptional point is limited by the number of degrees of freedom of a non-Hermitian system. In this letter, we refute this common opinion and show that non-Markovian effects can lead to dynamics characteristic of systems with exceptional points of higher orders than the number of degrees of freedom in the system. This takes place when the energy returns from reservoir to the system such that the dynamics of the system are divided into intervals in which it describes by the product of the exponential and a polynomial function of ever-increasing order. We demonstrate that by choosing the observation time, it is possible to observe exceptional points of arbitrary high orders. - oai:arXiv.org:2512.09582v1 + 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 quant-ph + cond-mat.mes-hall physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Timofey T. Sergeev, Evgeny S. Andrianov, Alexander A. Zyablovsky + Hao-Tian Li, Hong-Bin Wang, Zi-Xu Lu, Jie Li - Graph-Based Bayesian Optimization for Quantum Circuit Architecture Search with Uncertainty Calibrated Surrogates - https://arxiv.org/abs/2512.09586 - arXiv:2512.09586v1 Announce Type: new -Abstract: Quantum circuit design is a key bottleneck for practical quantum machine learning on complex, real-world data. We present an automated framework that discovers and refines variational quantum circuits (VQCs) using graph-based Bayesian optimization with a graph neural network (GNN) surrogate. Circuits are represented as graphs and mutated and selected via an expected improvement acquisition function informed by surrogate uncertainty with Monte Carlo dropout. Candidate circuits are evaluated with a hybrid quantum-classical variational classifier on the next generation firewall telemetry and network internet of things (NF-ToN-IoT-V2) cybersecurity dataset, after feature selection and scaling for quantum embedding. We benchmark our pipeline against an MLP-based surrogate, random search, and greedy GNN selection. The GNN-guided optimizer consistently finds circuits with lower complexity and competitive or superior classification accuracy compared to all baselines. Robustness is assessed via a noise study across standard quantum noise channels, including amplitude damping, phase damping, thermal relaxation, depolarizing, and readout bit flip noise. The implementation is fully reproducible, with time benchmarking and export of best found circuits, providing a scalable and interpretable route to automated quantum circuit discovery. - oai:arXiv.org:2512.09586v1 + 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 quant-ph - cs.AI - cs.LG - cs.NE - cs.NI - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Prashant Kumar Choudhary, Nouhaila Innan, Muhammad Shafique, Rajeev Singh + Georgi Bebrov - Quantum Gradient Flow Algorithm for Symmetric Positive Definite Systems via Quantum Eigenvalue Transformation: Towards Quantum CAE - https://arxiv.org/abs/2512.09623 - arXiv:2512.09623v1 Announce Type: new -Abstract: In this study, we propose the Quantum Gradient Flow Algorithm (QGFA), a novel quantum algorithm for solving symmetric positive definite (SPD) linear systems based on the variational formulation and time-evolution dynamics. Conventional quantum linear solvers, such as the quantum matrix inverse algorithm (QMIA), focus on approximating the matrix inverse through quantum signal processing (QSP). However, QMIA suffers from a crucial drawback: its computational efficiency deteriorates as the condition number increases. In contrast, classical SPD linear solvers, such as the steepest descent and conjugate gradient methods, are known for their fast convergence, which stems from the variational optimization principle of SPD systems. Inspired by this, we develop QGFA, which obtains the solution vector through the gradient-flow process of the corresponding quadratic energy functional. To validate the proposed method, we apply QGFA to the displacement-based finite element method (FEM) for two-dimensional linear elastic problems under plane stress conditions. The algorithm demonstrates accurate convergence toward classical FEM solutions even with a moderate number of QSP phase factors. Compared with QMIA, QGFA achieves lower relative errors and faster convergence when initialized with suitable initial states, demonstrating its potential as an efficient preconditioned quantum linear solver. The proposed framework provides a physically interpretable connection between classical iterative solvers and quantum computational paradigms. These findings suggest that QGFA can serve as a foundation for future developments in Quantum Computer-Aided Engineering (Quantum CAE), including nonlinear and multiphysics simulations. - oai:arXiv.org:2512.09623v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Yuto Lewis Terashima, Tadashi Kadowaki, Yohichi Suzuki, Mayu Muramatsu, Katsuhiro Endo + Pei-Zhe Li, Soumyakanti Bose, Hyunseok Jeong, William J. Munro, Kae Nemoto, Nicol\`o Lo Piparo - Geometric Origin of Quantum Entanglement - https://arxiv.org/abs/2512.09640 - arXiv:2512.09640v1 Announce Type: new -Abstract: We investigate massless representations related to the extension of Poincar\`e group constructed in [1]. These representations differ from Wigner's ones of standard Poincar\`e group because the stabilizer of lightlike orbits has extra degrees of freedom. The unitary irreducible representations (UIRs) of massless particles in this extension must decompose as a direct sum of a massless forward (positive zeroth component momentum) and massless backward (negative zeroth component momentum) Wigner's representations linked by internal two valued degree of freedom. We prove that these representations are unitarily equivalent to entangled states of two qubits. This provides a geometric origin of quantum entanglement for photons in the framework of quantum field theory: photons appear as superpositions of backward and forward propagating electromagnetic waves depending on a two valued parameter and this dependency gives rise to correlations between the values of local observables identical to those experienced with an entangled state of two qubits. Finally we describe an experiment capable of distinguishing the two different values of the parameter that links backward and forward massless representations providing experimental falsification of the theory. - oai:arXiv.org:2512.09640v1 + 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 quant-ph - hep-th - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/publicdomain/zero/1.0/ - Marco Zaopo + 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 - Optyx: A ZX-based Python library for networked quantum architectures - https://arxiv.org/abs/2512.09648 - arXiv:2512.09648v1 Announce Type: new -Abstract: Distributed, large-scale quantum computing will need architectures that combine matter-based qubits with photonic links, but today's software stacks target either gate-based chips or linear-optical devices in isolation. We introduce Optyx, an open-source Python framework offering a unified language to program, simulate, and prototype hybrid, networked systems: users create experiments that mix qubit registers, discrete-variable photonic modes, lossy channels, heralded measurements, and real-time feedback; Optyx compiles them via ZX/ZW calculus into optimised tensor-network forms, and executes with state-of-the-art contraction schedulers based on Quimb and Cotengra. Benchmarking on exact multi-photon circuit simulations shows that, versus permanent-based methods, tensor network contraction can deliver speedups of orders of magnitude for low-depth circuits and entangled photon sources, and natively supports loss and distinguishability -- establishing it as both a high-performance simulator and a rapid-prototyping environment for next-generation photonic-network experiments. - oai:arXiv.org:2512.09648v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Mateusz Kupper, Richie Yeung, Boldizs\'ar Po\'or, Alexis Toumi, William Cashman, Giovanni de Felice + Lucas H. English, Sam Roberts, Stephen D. Bartlett, Andrew C. Doherty, Dominic J. Williamson - Entanglement with a mode observable via a tunable interaction with a qubit - https://arxiv.org/abs/2512.09658 - arXiv:2512.09658v1 Announce Type: new -Abstract: We study the possibility of detection of ``spin-boson'' entanglement by qubit only measurements. Such entanglement is impossible to detect by previously proposed schemes that involve a fixed system-environment interaction, because of inherent symmetries within the coupling and the initial state of the environment. We take advantage of the possibility of tuning of qubit-environment coupling, that is available in some qubit realizations. As an example we study a superconducting transmon qubit interacting with a microwave cavity, which is one of such systems and is, furthermore, essential in the context of quantum information processing. We propose suitable Hamiltonian parameters for the preparation and measurement phases of the detection scheme that allow for an experimental test, and verify that the reported signal is nonnegligibly large still at finite temperatures. - oai:arXiv.org:2512.09658v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ma{\l}gorzata Strza{\l}ka, Radim Filip, Katarzyna Roszak + Peter Chernev, Andon A. Rangelov - Pattern Based Quantum Key Distribution using the five qubit perfect code for eavesdropper detection - https://arxiv.org/abs/2512.09672 - arXiv:2512.09672v1 Announce Type: new -Abstract: I propose a new quantum key distribution protocol that uses the five qubit error correction code to detect the presence of eavesdropper reliably. The protocol turns any information theoretical attacks into a classical guess about the pattern. The logical qubit is encoded with a specific pattern into a block of five physical qubits. The security of the protocol relies on the correct pattern choice of Alice and Bob. Decoding with any wrong pattern choice increases multi qubit error rate and the 5 qubit code transforms an eavesdropper's logical disturbance into a signature that is detectable and distinguishable from natural channel noise up to a certain distance. - oai:arXiv.org:2512.09672v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 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 + + + 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 + quant-ph + Fri, 12 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 + + + 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 + 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/ - Mehedi Hasan Rumi + Mladen Pavicic - Three-body interaction in a magnon-Andreev-superconducting qubit system: collapse-revival phenomena and entanglement redistribution - https://arxiv.org/abs/2512.09697 - arXiv:2512.09697v1 Announce Type: new -Abstract: Three-body interactions are fundamental for realizing novel quantum phenomena beyond pairwise physics, yet their implementation -- particularly among distinct quantum systems -- remains challenging. Here, we propose a hybrid quantum architecture comprising a magnonic mode (in a YIG sphere), an Andreev spin qubit (ASQ), and a superconducting qubit (SCQ), to realize a strong three-body interaction at the single-quantum level. Leveraging the spin-dependent supercurrent and circuit-integration flexibility of the ASQ, it is possible to engineer a strong tripartite coupling that jointly excites both qubits upon magnon annihilation (or excites magnons and SCQs upon ASQ deexcitation). Through analytical and numerical studies, we demonstrate that this interaction induces synchronized collapse and revival in qubit populations when the magnon is initially prepared in a coherent state. Notably, during the collapse region -- where populations remain static -- the entanglement structure undergoes a dramatic and continuous reorganization. We show that the genuine tripartite entanglement is redistributed into bipartite entanglement between the two qubits, and vice versa, with the total entanglement conserved. These phenomena, unattainable via two-body couplings, underscore the potential of three-body interactions for exploring intrinsically new quantum effects and advancing hybrid quantum information platforms. - oai:arXiv.org:2512.09697v1 + 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.mes-hall - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.stat-mech + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sheng Zhao, Peng-Bo Li + Anastasiia Tiutiakina - Device Independent Quantum Secret Sharing Using Multiparty Pseudo-telepathy Game - https://arxiv.org/abs/2512.09699 - arXiv:2512.09699v1 Announce Type: new -Abstract: Device-independent quantum secret sharing (DI-QSS) is a cryptographic protocol that overcomes the security limitations posed by untrusted quantum devices. We propose a DI-QSS protocol based on the multipartite pseudo-telepathy parity game, which achieves device-independence with simultaneous key generation without requiring dedicated test rounds, unlike CHSH-based schemes [Zhang et al., Phys. Rev. A, 2024]. Notably, the proposed scheme allows simultaneous device-independence verification and key-generation phases, achieving optimal performance for a seven-qubit GHZ state configuration. Further, we analyse the security of our protocol against collective attack and establish reduced resource requirement for the same length of the raw key compared to the previous protocol. Finally, we show that our protocol remains robust even in a noisy environment. - oai:arXiv.org:2512.09699v1 + 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 quant-ph - cs.CR - Thu, 11 Dec 2025 00:00:00 -0500 + gr-qc + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Santanu Majhi, Goutam Paul + Karol Sajnok, Kacper D\k{e}bski, Andrzej Dragan + + + 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 + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Tianyan Quantum Group - Dynamic stimulated emission for deterministic addition and subtraction of propagating photons - https://arxiv.org/abs/2512.09711 - arXiv:2512.09711v1 Announce Type: new -Abstract: Photon subtraction and addition are essential non-Gaussian processes in quantum optics, where conventional methods using linear optics and number-resolving detection often suffer from low success probability. Here, we introduce the concept of \textit{dynamic stimulated emission}, whereby a quantum emitter undergoes stimulated emission with a time-dependent coupling. We show that, for both two- and three-level emitters, this process can be used to deterministically add or subtract a photon to a single propagating optical mode. We provide semi-analytic solutions to this problem for Fock states, enabling deterministic and unconditional single-photon subtraction and addition with fidelity ${\cal F}>0.996$. Our semi-analytic solutions are provided for both dynamically coupled two-level systems and for three-level systems whose dynamical coupling is controlled by a coherent laser drive. Moving beyond individual Fock states, we further showcase the ability to subtract and add single photons to photon-number superposition states. We show that Schr\"{o}dinger cat states can be prepared from squeezed vacuum input via cascaded subtraction or cascaded addition. Finally, we show that our photon-addition process can be used to add a photon to any squeezed and displaced state with high success probability and fidelity ${\cal F}>0.99$, thereby potentially converting quantum emitters from single-photon sources to sources of single-photon-added Gaussian states without the need for inline squeezing. Our protocols provide a path towards integrating quantum emitters to construct efficient sources of single-mode non-Gaussian light beyond single photons. - oai:arXiv.org:2512.09711v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Haoyuan Luo, Parth S. Shah, Frank Yang, Mohammad Mirhosseini, Sahand Mahmoodian + Shuva Mondal, Priya Ghosh, Ujjwal Sen - Quantum random number generation from the continuous variable payload for the SPOQC mission - https://arxiv.org/abs/2512.09716 - arXiv:2512.09716v1 Announce Type: new -Abstract: The necessity of random numbers for various tasks, from simulation to cryptography, is crucial and immense. Here we demonstrate CV-QRNG using the CV payload of the SPOQC mission. The homodyne setup for QRNG uses the laser from the payload, in addition to potentially being used as detector in the case of an uplink scenario. Here we quantify the extractable secure randomness from the QRNG setup, that involves homodyne measurement of the vacuum states. The extracted randomness is tested against NIST test suite in addition to formally upper bounding the min-entropy. With the raw key length being $\approx1$ Mb in a given satellite pass, we get a total length of $\approx19.5$ Kb of certified random numbers from the 12-bit ADC. - oai:arXiv.org:2512.09716v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Vinod N. Rao, Killian Murphy, Fadi Ahwal, Emma Tien Hwai Medlock, Timothy P. Spiller, Rupesh Kumar + Tara Kit, Kimsay Pov, Myeongseong Go, Leanghok Hour, Arim Ryou, Kiwoong Kim, Tae-Kyung Kim, Youngsun Han - Quantumness certification via non-demolition measurements - https://arxiv.org/abs/2512.09734 - arXiv:2512.09734v1 Announce Type: new -Abstract: The fundamental question of when a static or dynamic system should be deemed intrinsically quantum remains a challenge to address in absolute terms. A rigorous criterion, however, can be established by focusing on the measurable or reconstructible features of the system. This determination transcends mere issues of a system's classical simulability or computational complexity. Instead, the critical requirement lies in the certification (ideally, in real-time) of the emergence and persistence of genuine quantum features, principally entanglement and quantum superposition. Quantum Non-Demolition Measurements (QNDM) serve as the appropriate instrument for this certification, both from a theoretical and experimental standpoint. In this review paper, we demonstrate, with accessible clarity, how the implementation of QNDM can be directly linked to a necessary and sufficient condition for the violation of macrorealism in finite-dimensional systems, establishing a conceptual parallel with Leggett-Garg inequalities. Using concrete examples that detail the detection of negative terms in the quasi-probability density function resulting from QNDM, we introduce the core concepts for certifying genuinely quantum features. As specific examples, we discuss an application where the quantum-to-classical transition due to the interaction with an environment can be tracked by QNDM. Moreover, we argue about the robustness of QNDM protocols in the presence of noise sources and their advantages with respect to the Leggett-Garg inequalities. Because of its straightforward implementation, the QNDM approach can be of direct relevance to both the foundations of quantum mechanics and quantum information theory, where a controlled generation and certification of genuinely quantum resources is a central concern. - oai:arXiv.org:2512.09734v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + physics.app-ph + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Paolo Solinas, Stefano Gherardini + Suwan I. Kang, Minhyeok Kim, Sanghyo Park, Heonsik Lee, Keunyoung Lee, Donggyu Kim - Quantum error correction via purification using a single auxiliary - https://arxiv.org/abs/2512.09745 - arXiv:2512.09745v1 Announce Type: new -Abstract: We propose a single auxiliary-assisted purification-based framework for quantum error correction, capable of correcting errors that drive a system from its ground-state subspace into excited-state sectors. The protocol consists of a joint time evolution of the system-auxiliary duo under a specially engineered interaction Hamiltonian, followed by a single measurement of the auxiliary in its energy eigenbasis and a subsequent post-selection of one of the measurement outcomes. We show that the resulting purified state always achieves unit fidelity, while the probability of obtaining any energy of the auxiliary other than its ground state energy yields the success rate of the protocol. We demonstrate the power of this proposed method for several low-distance quantum codes, including the three-, four-, and five-qubit codes, and for the one-dimensional isotropic Heisenberg model, subjected to bit-flip, phase-flip, and amplitude-damping noises acting on all qubits. Notably, the protocol expands the class of correctable errors for a given code, particularly in the presence of amplitude-damping noise. We further analyze the impact of replacing the auxiliary qudit with a single auxiliary qubit, and the changes in the performance of the protocol under the realistic scenario where noise remains active during the correction cycle. - oai:arXiv.org:2512.09745v1 + 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 quant-ph - cond-mat.str-el - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Chandrima B. Pushpan, Tanoy Kanti Konar, Aditi Sen De, Amit Kumar Pal + http://creativecommons.org/licenses/by/4.0/ + Or Peretz, Michal Koren, Nir Perel - Rotational excitation of molecules in the regime of strong ro-vibrational coupling: Comparison between an optical centrifuge and a transform-limited pulse - https://arxiv.org/abs/2512.09746 - arXiv:2512.09746v1 Announce Type: new -Abstract: We investigate theoretically the ability of an optical centrifuge - a laser pulse whose linear polarization is rotating at an accelerated rate, to control molecular rotation in the regime when the rigid-rotor approximation breaks down due to coupling between the vibrational and rotational degrees of freedom. Our analysis demonstrates that the centrifuge field enables controlled excitation of high rotational states while maintaining relatively low spread along the vibrational coordinate. We contrast this to the rotational excitation by a linearly polarized Gaussian pulse of equal spectral width and pulse energy which, although comparable to the centrifuge-induced rotation, is unavoidably accompanied by a substantial broadening of the vibrational wavepacket. - oai:arXiv.org:2512.09746v1 + 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 quant-ph - physics.atom-ph - physics.chem-ph - physics.comp-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - J. M. Garc\'ia-Garrido, V. Milner, C. P. Koch, R. Gonz\'alez-F\'erez + Tommaso Favalli, \v{Z}an Kokalj, Andrea Trombettoni - Optimal certification of constant-local Hamiltonians - https://arxiv.org/abs/2512.09778 - arXiv:2512.09778v1 Announce Type: new -Abstract: We study the problem of certifying local Hamiltonians from real-time access to their dynamics. Given oracle access to $e^{-itH}$ for an unknown $k$-local Hamiltonian $H$ and a fully specified target Hamiltonian $H_0$, the goal is to decide whether $H$ is exactly equal to $H_0$ or differs from $H_0$ by at least $\varepsilon$ in normalized Frobenius norm, while minimizing the total evolution time. We introduce the first intolerant Hamiltonian certification protocol that achieves optimal performance for all constant-locality Hamiltonians. For general $n$-qubit, $k$-local, traceless Hamiltonians, our procedure uses $O(c^k/\varepsilon)$ total evolution time for a universal constant $c$, and succeeds with high probability. In particular, for $O(1)$-local Hamiltonians, the total evolution time becomes $\Theta(1/\varepsilon)$, matching the known $\Omega(1/\varepsilon)$ lower bounds and achieving the gold-standard Heisenberg-limit scaling. Prior certification methods either relied on implementing inverse evolution of $H$, required controlled access to $e^{-itH}$, or achieved near-optimal guarantees only in restricted settings such as the Ising case ($k=2$). In contrast, our algorithm requires neither inverse evolution nor controlled operations: it uses only forward real-time dynamics and achieves optimal intolerant certification for all constant-locality Hamiltonians. - oai:arXiv.org:2512.09778v1 + 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 quant-ph - cs.CC - cs.DS - cs.IT cs.LG - math.IT - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Junseo Lee, Myeongjin Shin + http://creativecommons.org/licenses/by/4.0/ + Tobias Rohe, Markus Baumann, Michael Poppel, Gerhard Stenzel, Maximilian Zorn, Claudia Linnhoff-Popien - Pinball: A Cryogenic Predecoder for Quantum Error Correction Decoding Under Circuit-Level Noise - https://arxiv.org/abs/2512.09807 - arXiv:2512.09807v1 Announce Type: new -Abstract: Scaling fault tolerant quantum computers, especially cryogenic systems, to millions of qubits is challenging due to poorly-scaling data processing and power consumption overheads. One key challenge is the design of decoders for real-time quantum error correction (QEC), which demands high data rates for error processing; this is particularly apparent in systems with cryogenic qubits and room temperature (RT) decoders. In response, cryogenic predecoding using lightweight logic has been proposed to handle common, sparse errors in the cryogenic domain. However, prior work only accounts for a subset of error sources present in real-world quantum systems with limited accuracy, often degrading performance below a useful level in practical scenarios. Furthermore, prior reliance on SFQ logic precludes detailed architecture-technology co-optimization. - To address these shortcomings, this paper introduces Pinball, a comprehensive design in cryogenic CMOS of a QEC predecoder tailored to realistic, circuit-level noise. By accounting for error generation and propagation through QEC circuits, our design achieves higher predecoding accuracy, outperforming logical error rates (LER) of the current state-of-the-art cryogenic predecoder by nearly six orders of magnitude. Remarkably, despite operating under much stricter power and area constraints, Pinball also reduces LER by 32.58x and 5x, respectively, compared to the state-of-the-art RT predecoder and RT ensemble configurations. By increasing cryogenic coverage, we also reduce syndrome bandwidth up to 3780.72x. Through co-design with 4 K-characterized 22 nm FDSOI technology, we achieve a peak power consumption under 0.56 mW. Voltage/frequency scaling and body biasing enable 22.2x lower typical power consumption, yielding up to 67.4x total energy savings. Assuming a 4 K power budget of 1.5 W, our predecoder supports up to 2,668 logical qubits at d=21. - oai:arXiv.org:2512.09807v1 + 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 quant-ph - cs.AR - cs.ET - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.str-el + Fri, 12 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Tong Liu, Hui-Ke Jin, Tao Xiang, Hong-Hao Tu + + + 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 + quant-ph + physics.optics + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alexander Knapen, Guanchen Tao, Jacob Mack, Tomas Bruno, Mehdi Saligane, Dennis Sylvester, Qirui Zhang, Gokul Subramanian Ravi + 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 - Quantum Algorithm for Estimating Ollivier-Ricci Curvature - https://arxiv.org/abs/2512.09822 - arXiv:2512.09822v1 Announce Type: new -Abstract: We introduce a quantum algorithm for computing the Ollivier Ricci curvature, a discrete analogue of the Ricci curvature defined via optimal transport on graphs and general metric spaces. This curvature has seen applications ranging from signaling fragility in financial networks to serving as basic quantities in combinatorial quantum gravity. For inputs given as a point cloud with pairwise distances, we show that our algorithm can achieve an exponential speedup over the best-known classical methods for two particular classes of problem. Our work is another step toward quantum algorithms for geometrical problems that are capable of delivering practical value while also informing fundamental theory. - oai:arXiv.org:2512.09822v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Nhat A. Nghiem, Linh Nguyen, Tuan K. Do, Tzu-Chieh Wei, Trung V. Phan + Ignacio B. Acedo, Pablo Rodriguez-Grasa, Pablo Garcia-Azorin, Javier Gonzalez-Conde - Transpiling quantum circuits by a transformers-based algorithm - https://arxiv.org/abs/2512.09834 - arXiv:2512.09834v1 Announce Type: new -Abstract: Transformers have gained popularity in machine learning due to their application in the field of natural language processing. They manipulate and process text efficiently, capturing long-range dependencies among data and performing the next word prediction. On the other hand, gate-based quantum computing is based on controlling the register of qubits in the quantum hardware by applying a sequence of gates, a process which can be interpreted as a low level text programming language. We develop a transformer model capable of transpiling quantum circuits from the qasm standard to other sets of gates native suited for a specific target quantum hardware, in our case the set for the trapped-ion quantum computers of IonQ. The feasibility of a translation up to five qubits is demonstrated with a percentage of correctly transpiled target circuits equal or superior to 99.98%. Regardless the depth of the register and the number of gates applied, we prove that the complexity of the transformer model scales, in the worst case scenario, with a polynomial trend by increasing the depth of the register and the length of the circuit, allowing models with a higher number of parameters to be efficiently trained on HPC infrastructures. - oai:arXiv.org:2512.09834v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Michele Banfi, Paolo Zentilini, Sebastiano Corli, Enrico Prati + 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 - Practical and Efficient Verification of Entanglement with Incomplete Measurement Settings - https://arxiv.org/abs/2512.09856 - arXiv:2512.09856v1 Announce Type: new -Abstract: In this work, we present a practical and efficient framework for verifying entangled states when only a tomographically incomplete measurement setting is available-specifically, when access to observables is severely limited. We show how the experimental estimation of a small number of observables can be directly exploited to construct a large family of entanglement witnesses, enabling the efficient identification of entangled states. Moreover, we introduce an optimization approach, formulated as a semidefinite program, that systematically searches for those witnesses best suited to reveal entanglement under the given measurement constraints. We demonstrate the practicality of the approach in a proof-of-principle experiment with photon-polarization qubits, where entanglement is certified using only a fraction of the full measurement data. These results reveal the maximal usefulness of incomplete measurement settings for entanglement verification in realistic scenarios. - oai:arXiv.org:2512.09856v1 + 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 quant-ph - physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Jiheon Seong, Jin-Woo Kim, Seungchan Seo, Seung-Hyun Nam, Anindita Bera, Dariusz Chru\'sci\'nski, June-Koo Kevin Rhee, Heonoh Kim, Joonwoo Bae + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Evan E Dobbs, Nicolas Delfosse, Aharon Brodutch - True Random Number Generators on IQM Spark - https://arxiv.org/abs/2512.09862 - arXiv:2512.09862v1 Announce Type: new -Abstract: Random number generation is fundamental for many modern applications including cryptography, simulations and machine learning. Traditional pseudo-random numbers may offer statistical unpredictability, but are ultimately deterministic. On the other hand, True Random Number Generation (TRNG) offers true randomness. One way of obtaining such randomness are quantum systems, including quantum computers. As such the use of quantum computers for TRNG has received considerable attention in recent years. However, existing studies almost exclusively consider IBM quantum computers, often stop at using simulations and usually test only a handful of different TRNG quantum circuits. In this paper, we address those issues by presenting a study of TRNG circuits on Odra 5 a real-life quantum computer installed at Wroc{\l}aw University of Science and Technology. It is also the first study to utilize the IQM superconducting architecture. Since Odra 5 is available on-premises it allows for much more comprehensive study of various TRNG circuits. In particular, we consider 5 types of TRNG circuits with 105 circuit subvariants in total. Each circuit is used to generate 1 million bits. We then perform an analysis of the quality of the obtained random sequences using the NIST SP 800-22 and NIST SP 800-90B test suites. We also provide a comprehensive review of existing literature on quantum computer-based TRNGs. - oai:arXiv.org:2512.09862v1 + 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 quant-ph - cs.CR - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Andrzej Gnatowski, Jaros{\l}aw Rudy, Teodor Ni\.zy\'nski, Krzysztof \'Swi\k{e}cicki + http://creativecommons.org/licenses/by/4.0/ + Wen-Han Png, Xueyuan Hu, Valerio Scarani - Error Mitigation of Fault-Tolerant Quantum Circuits with Soft Information - https://arxiv.org/abs/2512.09863 - arXiv:2512.09863v1 Announce Type: new -Abstract: Quantum error mitigation (QEM) is typically viewed as a suite of practical techniques for today's noisy intermediate-scale quantum devices, with limited relevance once fault-tolerant quantum computers become available. In this work, we challenge this conventional wisdom by showing that QEM can continue to provide substantial benefits in the era of quantum error correction (QEC), and in an even more efficient manner than it does on current devices. We introduce a framework for logical-level QEM that leverages soft information naturally produced by QEC decoders, requiring no additional data, hardware modifications, or runtime overhead beyond what QEC protocols already provide. Within this framework, we develop and analyze three logical-level QEM techniques: post-selection and runtime abort policies, probabilistic error cancellation, and zero-noise extrapolation. Our techniques reduce logical error rates by more than 100x while discarding fewer than 0.1% of shots; they also provide in situ characterization of logical channels for QEM protocols. As a proof of principle, we benchmark our approach using a surface-code architecture and two state-of-the-art decoders based on tensor-network contraction and minimum-weight perfect matching. We evaluate logical-level QEM on random Clifford circuits and molecular simulation algorithms and find that, compared to previous approaches relying on QEC only or QEC combined with QEM, we can achieve up to 87.4% spacetime overhead savings. Our results demonstrate that logical-level QEM with QEC decoder soft information can reliably improve logical performance, underscoring the efficiency and usefulness of QEM techniques for fault-tolerant quantum computers. - oai:arXiv.org:2512.09863v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + physics.optics + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Zeyuan Zhou, Shaun Pexton, Aleksander Kubica, Yongshan Ding + 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 - Tomographic characterization of non-Hermitian Hamiltonians in reciprocal space - https://arxiv.org/abs/2512.09870 - arXiv:2512.09870v1 Announce Type: new -Abstract: Non-Hermitian Hamiltonians enrich quantum physics by extending conventional phase diagrams, enabling novel topological phenomena, and realizing exceptional points with potential applications in quantum sensing. Here, we present an experimental photonic platform capable of simulating a non-unitary quantum walk generated by a peculiar type of non-Hermitian Hamiltonian, largely unexplored in the literature. The novelty of this platform lies in its direct access to the reciprocal space, which enables us to scan the quasi-momentum across the entire Brillouin zone and thus achieve a precise tomographic reconstruction of the underlying non-Hermitian Hamiltonian, indicated by the comparison between theoretical predictions and experimental measurements. From the inferred Hamiltonian, it is possible to retrieve complex-valued band structures, resolve exceptional points in momentum space, and detect the associated parity-time symmetry breaking through eigenvector coalescence. Our results, presented entirely in quasi-momentum space, represent a substantial shift in perspective in the study of non-Hermitian phenomena. - oai:arXiv.org:2512.09870v1 + 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 quant-ph - cond-mat.mes-hall - Thu, 11 Dec 2025 00:00:00 -0500 + cs.CC + stat.AP + Fri, 12 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Francesco Di Colandrea, Fabrizio Pavan, Sarvesh Bansal, Paola Savarese, Grazia Di Bello, Giulio De Filippis, Carmine Antonio Perroni, Donato Farina, Filippo Cardano + http://creativecommons.org/licenses/by/4.0/ + Gil Kalai, Tomer Shoham, Carsten Voelkmann - A 0.8395-approximation algorithm for the EPR problem - https://arxiv.org/abs/2512.09896 - arXiv:2512.09896v1 Announce Type: new -Abstract: We give an efficient 0.8395-approximation algorithm for the EPR Hamiltonian. Our improvement comes from a new nonlinear monogamy-of-entanglement bound on star graphs and a refined parameterization of a shallow quantum circuit from previous works. We also prove limitations showing that current methods cannot achieve substantially better approximation ratios, indicating that further progress will require fundamentally new techniques. - oai:arXiv.org:2512.09896v1 + 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 quant-ph - cs.DS - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.mes-hall + cond-mat.mtrl-sci + Fri, 12 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Anuj Apte, Eunou Lee, Kunal Marwaha, Ojas Parekh, Lennart Sinjorgo, James Sud + Jonah Nagura, Mykyta Onizhuk, Giulia Galli - Two simple models derived from a quantum-mechanical particle on an elliptical path - https://arxiv.org/abs/2512.09905 - arXiv:2512.09905v1 Announce Type: new -Abstract: We analyze two simple models derived from a quantum-mechanical particle on an elliptical path. The first Hamiltonian operator is non-Hermitian but isomorphic to an Hermitian operator. It appears to exhibit the same two-fold degeneracy as the particle on a circular path. More precisely, $E_n=n^2E_1,\ n=1,2,\ldots$ (in addition to an exact eigenvalue $E_0=0$). The second Hamiltonian operator is Hermitian and does not exhibit such degeneracy. In this case the nth excited energy level splits at the nth order of perturbation theory. Both models can be described in terms of the same point-group symmetry. - oai:arXiv.org:2512.09905v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Francisco M. Fern\'andez + Francesco Hoch, Taira Giordani, Gonzalo Carvacho, Nicol\`o Spagnolo, Fabio Sciarrino - A Hierarchy of Entanglement Cones via Rank-Constrained $C^*$-Convex Hulls - https://arxiv.org/abs/2512.05560 - arXiv:2512.05560v1 Announce Type: cross -Abstract: This paper systematically investigates the geometry of fundamental quantum cones, the separable cone ($\mathscr{P}_+$) and the Positive Partial Transpose (PPT) cone ($\mathcal{P}_{\mathrm{PPT}}$), under generalized non-commutative convexity. We demonstrate a sharp stability dichotomy analyzing $C^*$-convex hulls of these cones: while $\mathscr{P}_+$ remains stable under local $C^*$-convex combinations, its global $C^*$-convex hull collapses entirely to the cone of all positive semidefinite matrices, $\operatorname{MCL}(\mathscr{P}_+) = \mathscr{P}_0$. To gain finer control and classify intermediate structures, we introduce the concept of ``$k$-$C^*$-convexity'', by using the operator Schmidt rank of $C^*$-coefficients. This constraint defines a new hierarchy of nested intermediate cones, $\operatorname{MCL}_k(\cdot)$. We prove that this hierarchy precisely recovers the known Schmidt number cones for the separable case, establishing a generalized convexity characterization: $\operatorname{MCL}_k(\mathscr{P}_+) = \mathcal{T}_k$. Applied to the PPT cone, this framework generates a family of conjectured non-trivial intermediate cones, $\mathcal{C}_{\mathrm{PPT}, k}$. - oai:arXiv.org:2512.05560v1 - math-ph - math.FA - math.MP + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + cs.LG + Fri, 12 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Mohsen Kian + 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 - Internal spaces of fermion and boson fields, described with the superposition of odd and even products of $\gamma^{a}$, enable understanding of all the second-quantised fields in an equivalent way - https://arxiv.org/abs/2512.09008 - arXiv:2512.09008v1 Announce Type: cross -Abstract: Using the odd and even ``basis vectors'', which are the superposition of odd and even products of $\gamma^a$'s, to describe the internal spaces of the second quantised fermion and boson fields, respectively, offers in even-dimensional spaces, like it is $d=(13+1)$, the unique description of all the properties of the observed fermion fields (quarks and leptons and antiquarks and antileptons appearing in families) and boson fields (gravitons, photons, weak bosons, gluons and scalars) in a unique way, providing that all the fields have non zero momenta only in $d =(3+1)$ of the ordinary space-time, bosons have the space index $\alpha$ (which is for tensors and vectors $\mu =(0,1,2,3)$ and for scalars $\sigma \ge 5$). In any even-dimensional space, there is the same number of internal states of fermions appearing in families and their Hermitian conjugate partners as it is of the two orthogonal groups of boson fields having the Hermitian conjugate partners within the same group. A simple action for massless fermion and boson fields describes all the fields uniquely. The paper overviews the theory, presents new achievements and discusses the open problems of this theory. - oai:arXiv.org:2512.09008v1 - hep-th + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + physics.data-an + Fri, 12 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 + + + 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 + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - N. S. Manko\v{c} Bor\v{s}tnik + Benjamin Anker, Dripto M. Debroy - Swimming against a superfluid flow: Self-propulsion via vortex-antivortex shedding in a quantum fluid of light - https://arxiv.org/abs/2512.09028 - arXiv:2512.09028v1 Announce Type: cross -Abstract: A superfluid flows without friction below a critical velocity, exhibiting zero drag force on impurities. Above this threshold, superfluidity breaks down, and the internal energy is redistributed into incoherent excitations such as vortices. We demonstrate that a finite-mass, mobile impurity immersed in a flowing two-dimensional paraxial superfluid of light can \textit{swim} against the superfluid current when this critical velocity is exceeded. This self-propulsion is achieved by the periodic emission of quantized vortex-antivortex pairs downstream, which impart an upstream recoil momentum that results in a net propulsive force. Analogous to biological systems that minimize effort by exploiting wake turbulence, the impurity harnesses this vortex backreaction as a passive mechanism of locomotion. Reducing the impurity dynamics to the motion of its center of mass and using a point-vortex model, we quantitatively describe how this mechanism depends on the impurity geometry and the surrounding flow velocity. Our findings establish a fundamental link between internal-energy dissipation in quantum fluids and concepts of self-propulsion in active-matter systems, and opens new possibilities for exploiting vortices for controlled quantum transport at the microscale. - oai:arXiv.org:2512.09028v1 - cond-mat.quant-gas - cond-mat.soft + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + Fri, 12 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - Myrann Baker-Rasooli, Tangui Aladjidi, Tiago D. Ferreira, Alberto Bramati, Mathias Albert, Pierre-\'Elie Larr\'e, Quentin Glorieux + Julio Del Castillo, Mats Granath, Evert van Nieuwenburg - Extreme statistics as a probe of the superfluid to Bose-glass Berezinskii-Kosterlitz-Thouless transition - https://arxiv.org/abs/2512.09029 - arXiv:2512.09029v1 Announce Type: cross -Abstract: Recent studies of delocalization-localization transitions in disordered quantum chains have highlighted the role of rare, chain-breaking events that favor localization, in particular for high-energy eigenstates related to many-body localization. In this context, we revisit the random-field XXZ spin-1/2 chain at zero temperature with ferromagnetic interactions, equivalent to interacting fermions or hard-core bosons in a random potential with attractive interactions. We argue that localization in this model can be characterized by chain-breaking events, which are probed by the extreme values of simple local observables, such as the on-site density or the local magnetization, that are readily accessible in both experiments and numerical simulations. Adopting a bosonic language, we study the disorder-induced Berezinskii-Kosterlitz-Thouless (BKT) quantum phase transition from superfluid (SF) to Bose glass (BG), and focus on the strong disorder regime where localization is driven by weak links. Based on high-precision density matrix renormalization group simulations, we numerically show that extreme local densities accurately capture the BKT transition, even for relatively short chains ranging from a few dozen to a hundred sites. We also discuss the SF-BG transition in the weak disorder regime, where finite-size effects pose greater challenges. Overall, our work seeks to establish a solid foundation for using extreme statistics of local observables, such as density, to probe delocalization-localization transitions in disordered quantum chains, both in the ground state and at high energy. - oai:arXiv.org:2512.09029v1 - cond-mat.dis-nn - cond-mat.quant-gas - cond-mat.str-el + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + Fri, 12 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - Jeanne Colbois, Natalia Chepiga, Shaffique Adam, Gabriel Lemari\'e, Nicolas Laflorencie + Piotr Masajada, Aby Philip, Alexander Streltsov - Beyond Ginibre statistics in open Floquet chaotic systems with localized leaks - https://arxiv.org/abs/2512.09038 - arXiv:2512.09038v1 Announce Type: cross -Abstract: We show that the spectral properties of driven quantum systems with a classically chaotic counterpart and spatially localized openness, such as optical or microwave billiards with leaks, deviate from predictions of Ginibre ensembles. Our analysis focuses on the leaky quantum standard map (QSM) of the kicked rotor. We compare its complex resonance spectrum with both Ginibre and truncated circular orthogonal ensembles (TCOEs). We find that the long-lived resonances follow TCOE statistics, reproducing the density of states and level spacing correlations, but depart from Ginibre predictions. Short-lived resonances, however, do not show a clear correspondence with either random-matrix ensemble. We also demonstrate that increasing the leak size takes the density of states of the TCOE toward the Ginibre limit, yet their spectral correlations remain distinct. - oai:arXiv.org:2512.09038v1 - cond-mat.stat-mech + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + physics.optics + Fri, 12 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Edson M. Signor, Miguel A. Prado Reynoso, Bidhi Vijaywargia, Sandra D. Prado, Lea F. Santos + Armine I. Dingilian, Aarnah Kurella, Cheyenne S. Mitchell, Dhananjay Dhruva, David J. Durden, Mikael P. Backlund - On modeling quantum point contacts in quantum Hall systems - https://arxiv.org/abs/2512.09045 - arXiv:2512.09045v1 Announce Type: cross -Abstract: Quantum point contacts (QPC) are a key instrument in investigating the physics of edge excitations in the quantum Hall effect. However, at not-so-high bias voltage values, the predictions of the conventional point QPC model often deviate from the experimental data both in the integer and (more prominently) in the fractional quantum Hall regime. One of the possible explanations for such behaviors is the dependence of the tunneling between the edges on energy, an effect not present in the conventional model. Here we introduce two models that take QPC spatial extension into account: wide-QPC model that accounts for the distance along which the edges are in contact; long-QPC model accounts for the fact that the tunneling amplitude originates from a finite bulk gap and a finite distance between the two edges. We investigate the predictions of these two models in the integer quantum Hall regime for the energy dependence of the tunneling amplitude. We find that these two models predict opposite dependences: the amplitude decreasing or increasing away from the Fermi level. We thus elucidate the effect of the QPC geometry on the energy dependence of the tunneling amplitude and investigate its implications for transport observables. - oai:arXiv.org:2512.09045v1 - cond-mat.mes-hall + 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 + 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 + + + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - cross + Fri, 12 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + V. Yu. Mylnikov, S. O. Potashin, Alex Kamenev + + + 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 + quant-ph + cs.CC + cs.IT + cs.LG + math.IT + Fri, 12 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Prasoon Kumar, Kyrylo Snizhko + Jordan Cotler, Weiyuan Gong, Ishaan Kannan - High-resolution broadband characterization of resonance dispersion in an optical microresonator - https://arxiv.org/abs/2512.09475 - arXiv:2512.09475v1 Announce Type: cross -Abstract: Accurate knowledge of the uneven free spectral range of an optical microresonator, which provides direct insight into group velocity dispersion, is essential for understanding and controlling Kerr frequency comb dynamics. In this work, we present a simple and highly precise method formeasuring the free spectral range over a 5 THz bandwidth in silicon nitride microresonators, leveraging a wavemeter with 0.4 MHz resolution. Our fully fibered plug-and-play experimental setup enables the accurate extraction of resonance frequencies. By carefully analyzing the spectral position of each resonance, we measure both second- and third-order free spectral range expansion coefficients. This approach offers a robust and accessible tool for dispersion characterization in integrated photonic circuits, paving the way for next-generation of Kerr comb sources and quantum photonic technologies. - oai:arXiv.org:2512.09475v1 - physics.optics + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross - http://creativecommons.org/licenses/by/4.0/ - Romain Dalidet, Adrien Bensemhoun, Gregory Sauder, Anthony Martin, David Medina, Carlos Alonso Ramos, Eric Cassan, Laurent Vivien, Jonathan Faugier Tovar, Baptiste Routier, Quentin Wilmart, S\'egol\`ene Olivier, Virginia D Auria, Laurent Labont\'e, S\'ebastien Tanzilli + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Yang Li, Chong Ma, Yuanzheng Li, Sen Li, Yanbo Chen, Zhaoyang Dong - Single particle dynamical signature of topology induced by single mode cavities in Su-Schrieffer-Heeger chain - https://arxiv.org/abs/2512.09520 - arXiv:2512.09520v1 Announce Type: cross -Abstract: Witnessing and tracking topological phase transitions induced by interactions with the environment is a crucial challenge. Among the various experimental approaches to detect topological properties, the Mean Chiral Displacement (MCD) has emerged as a powerful bulk probe in one-dimensional chiral systems, allowing the extraction of the topological invariant from single-particle dynamics. Here we study the dynamics of a single particle in a one-dimensional Su-Schrieffer-Heeger chain coupled to multiple cavity modes via inter-cell hopping terms, focusing on the out-of-equilibrium behavior of the MCD. We show that, whenever the frequency is larger than the static hopping amplitudes, the coupling induces a discontinuous jump in the MCD, already at small times, signaling that such a coupling also leaves a signature in the survival edge probability when the dynamics are initialized at one of the two edges. For frequencies comparable to the static hopping amplitudes, topological order competes with dissipative effects, which makes the MCD behave smoothly, retaining information about the driven-dissipative topology. - oai:arXiv.org:2512.09520v1 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Fabrizio Pavan, Grazia Di Bello, Giulio De Filippis, Carmine Antonio Perroni + Phil Attard - Unified theory of local integrals of motion - https://arxiv.org/abs/2512.09595 - arXiv:2512.09595v1 Announce Type: cross -Abstract: Many-body localization (MBL) is understood theoretically through the existence of an extensive number of local integrals of motion (LIOMs). These conserved quantities are related to the microscopic quantum degrees of freedom that are spatially localized. Here, we present a general framework for constructing exact LIOMs with the desired locality and quantum numbers supplied as input rather than arising as emergent properties. We show that one can express the task of finding LIOMs as an optimization problem. In simple cases, solving this problem amounts to matrix diagonalization, while in more complex settings, it connects to the question of finding classical ground states of spin-glass models. We illustrate our theory using paradigmatic examples of single-particle Anderson localization and MBL in interacting spin chains. These developments unify previous results and reveal intriguing connections among many-body localization, spin-glass physics and constrained optimization problems. - oai:arXiv.org:2512.09595v1 - cond-mat.dis-nn - math-ph - math.MP + 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 + cond-mat.str-el quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ben Craps, Oleg Evnin, Dmitry Kovrizhin, Gabriele Pascuzzi + Ammar Kirmani, Andrew A. Allocca, Jian-Xin Zhu, Armin Rahmani, Sriram Ganeshan, Pouyan Ghaemi - Programmable Assembly of Ground State Fermionic Tweezer Arrays - https://arxiv.org/abs/2512.09849 - arXiv:2512.09849v1 Announce Type: 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 \qty{20}{\us} exposure, and \qty{3}{\s} experimental cycles, these advances establish a fast, scalable, and programmable architecture for fermionic quantum simulation. - oai:arXiv.org:2512.09849v1 - cond-mat.quant-gas - physics.atom-ph + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Naman Jain, Jin Zhang, Marcus Culemann, Philipp M. Preiss + Parvinder Solanki, Igor Lesanovsky, Gabriele Perfetto - Photon emission by vortex particles accelerated in a linac - https://arxiv.org/abs/2512.09921 - arXiv:2512.09921v1 Announce Type: cross -Abstract: We study the photon emission by charged spinless particles with phase vortices and an orbital angular momentum (OAM) projection in longitudinal electric and magnetic fields within the scalar QED. A realistic wave packet of an electron or ion accelerated by a radio-frequency wave locally feels a constant and spatially homogeneous field, which allows us to develop an effective model for losing the angular momentum of the vortex particle due to photon emission. For the fields typical for accelerator facilities, we find that an effective lifetime of the vortex state greatly exceeds the acceleration time. This proves that the acceleration of vortex electrons, ions, muons, and so forth to relativistic energies is possible in conventional linacs, as well as in the wake-field accelerators with higher field gradients, the OAM losses due to the photon emission are mostly negligible, and that the vortex quantum state is highly robust against these losses. - oai:arXiv.org:2512.09921v1 - hep-ph - physics.acc-ph + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - A. Yu. Murtazin, G. K. Sizykh, D. V. Grosman, U. G. Rybak, A. A. Shchepkin, D. V. Karlovets + Dimitrios Kranas, Amaury Marchon, Silvia Pla - Connecting single-layer $t$-$J$ to Kondo lattice models: Exploration with cold atoms - https://arxiv.org/abs/2512.09926 - arXiv:2512.09926v1 Announce Type: cross -Abstract: The Kondo effect, a hallmark of many-body physics, emerges from the antiferromagnetic coupling between localized spins and conduction fermions, leading to a correlated many-body singlet state. Here we propose to use the mixed-dimensional (mixD) bilayer Hubbard geometry as a platform to study Kondo lattice physics with current ultracold atom experiments. At experimentally feasible temperatures, we predict that key features of the Kondo effect can be observed, including formation of the Kondo cloud around a single impurity and the competition of singlet formation with Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions for multiple impurities, summarized in the Doniach phase diagram. Moreover, we show that the mixD platform provides a natural bridge between the Doniach phase diagram of the Kondo lattice model, relevant to heavy-fermion materials, and the phase diagram of cuprate superconductors as described by a single-layer Zhang-Rice type $t$-$J$ model: It is possible to continuously tune between the two regimes by changing the interlayer Kondo coupling. Our findings demonstrate that the direct connection between high-temperature superconductivity and heavy-fermion physics can be experimentally studied using currently available quantum simulation platforms. - oai:arXiv.org:2512.09926v1 - cond-mat.quant-gas - cond-mat.str-el + 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 + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + S. Shajidul Haque, Ghadir Jafari, Bret Underwood + + + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hannah Lange, Eugene Demler, Jan von Delft, Annabelle Bohrdt, Fabian Grusdt + Ryan L. Mann, Gabriel Waite - Higher-dimensional Euclidean and non-Euclidean structures in planar circuit quantum electrodynamics - https://arxiv.org/abs/2108.08854 - arXiv:2108.08854v2 Announce Type: replace -Abstract: We show that a recent proposal for simulating planar hyperbolic lattices with circuit quantum electrodynamics can be extended to accommodate also higher dimensional lattices in Euclidean and non-Euclidean spaces if one allows for circuits with more than three polygons at each vertex. The quantum dynamics of these circuits, which can be constructed with present-day technology, are governed by effective tight-binding Hamiltonians corresponding to higher-dimensional Kagom\'{e}-like structures ($n$-dimensional zeolites), which are well known to exhibit strong frustration and flat bands. We analyze the relevant spectra of these systems and derive an exact expression for the fraction of flat-band states. Our results expand considerably the range of non-Euclidean geometry realizations with circuit quantum electrodynamics. - oai:arXiv.org:2108.08854v2 + 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 quant-ph + Fri, 12 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 + + + 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 - gr-qc - hep-th - Thu, 11 Dec 2025 00:00:00 -0500 - replace + physics.atm-clus + physics.chem-ph + physics.comp-ph + quant-ph + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Alberto Saa, Eduardo Miranda, Francisco Rouxinol + Ezekiel Oyeniyi, Omololu Akin-Ojo - Performance Analysis of Quantum CSS Error-Correcting Codes via MacWilliams Identities - https://arxiv.org/abs/2305.01301 - arXiv:2305.01301v3 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:2305.01301v3 + 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 quant-ph - cs.IT - math.IT - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Diego Forlivesi, Lorenzo Valentini, Marco Chiani + Magdalena Musat, Mikael R{\o}rdam - Quantum Communication Networks Enhanced by Distributed Quantum Memories - https://arxiv.org/abs/2403.16367 - arXiv:2403.16367v2 Announce Type: replace -Abstract: Building large-scale quantum communication networks has its unique challenges. Here, we demonstrate that a network-wide synergistic usage of quantum memories distributed in a quantum communication network offers a fundamental advantage. We first map the problem of quantum communication with local usage of memories into a classical continuum percolation model. Then, we show that this mapping can be improved through a cooperation of quantum distillation and relay protocols via remote access to distributed memories. This improved mapping, which we term $\alpha$-percolation, can be formulated in terms of graph-merging rules, analogous to the decimation rules of the renormalization group treatment of disordered quantum magnets. These rules can be performed in any order, yielding the same optimal result that is characterized by the emergence of a ``positive feedback'' mechanism and the formation of spatially disconnected ``hopping'' communication components -- both marking significant improvements beyond the traditional point-to-point consideration of quantum communication in networked structures. - oai:arXiv.org:2403.16367v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Xiangyi Meng, Nicol\`o Lo Piparo, Kae Nemoto, Istv\'an A. Kov\'acs + 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 - A simple fourth order propagator based on the Magnus expansion in the Liouville space: Application to a $\Lambda$-system and assessment of the rotating wave approximation - https://arxiv.org/abs/2407.03576 - arXiv:2407.03576v2 Announce Type: replace -Abstract: A simple 4th order propagator [Ture and Jang, {\it J. Phys. Chem. A.} {\bf 128}, 2871 (2024)] based on the Magnus expansion (ME) is extended to the Liouville space for both closed-system and Lindbladian open-system quantum dynamics. For both dynamics, commutator free versions of 4th order propagators are provided as well. These propagators are then applied to the dynamics of a driven $\Lambda$-system, where Lindblad terms represent the effect of a photonic bath. For both dynamics, the accuracy of the rotating wave approximation (RWA) for the matter-radiation interaction is assessed. We confirmed reasonable performance of RWA for weak and resonant fields. However, small errors appear for moderate fields and substantial errors can be found for strong fields where coherent population trapping can still be expected. We also found that the presence of bath for open system quantum dynamics consistently reduces the errors of the RWA. These results provide a quantitative information on how the RWA breaks down beyond weak field or for non-resonant cases. Major results are benchmarked against results of our 6th order ME-based propagator. We also provide numerical comparison of our algorithms with other 4th order algorithms for the $\Lambda$-system. These confirm reasonable performance of out simple propagators and the improvement gained through commutator-free expressions. - oai:arXiv.org:2407.03576v2 + 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 quant-ph - physics.atom-ph - physics.chem-ph - physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Taner M. Ture, Changbong Hyeon, Seogjoo J. Jang + Fri, 12 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 - A Novel Stabilizer-based Entanglement Distillation Protocol for Qudits - https://arxiv.org/abs/2408.02383 - arXiv:2408.02383v3 Announce Type: replace -Abstract: Entanglement distillation, the process of converting weakly entangled states into maximally entangled ones using Local Operations and Classical Communication (LOCC), is pivotal for robust entanglement-assisted quantum information processing in error-prone environments. A construction based on stabilizer codes offers an effective method for designing such protocols. By analytically investigating the effective action of stabilizer protocols for systems of prime dimension $d$, we establish a standard form for the output states of recurrent stabilizer-based distillation. This links the properties of input states, stabilizers, and encodings to the properties of the protocol. Based on those insights, we present a novel two-copy distillation protocol, applicable to all bipartite states in prime dimension, that maximizes the fidelity increase per iteration for Bell-diagonal states. The power of this framework and the protocol is demonstrated through numerical investigations, which provide evidence for superior performance in terms of efficiency and distillability of low-fidelity states compared to other well-established recurrence protocols. By elucidating the interplay between states, errors, and protocols, our contribution advances the systematic development of highly effective distillation protocols, enhancing our understanding of distillability. - oai:arXiv.org:2408.02383v3 + 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 + hep-ph + physics.comp-ph quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace - http://creativecommons.org/licenses/by/4.0/ - Christopher Popp, Tobias C. Sutter, Beatrix C. Hiesmayr + Fri, 12 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 - Multipartite entanglement vs nonlocality for two families of $N$-qubit states - https://arxiv.org/abs/2409.10888 - arXiv:2409.10888v2 Announce Type: replace -Abstract: Entangled states of multiple qubits can violate Bell-type inequalities indicating nonlocal behavior of multiqubit quantum correlations. We analyze the relation between multipartite entanglement and genuine multipartite nonlocality, characterized by Svetlichny inequality violations, for two families of $N-$qubit states. We show that for the generalized GHZ family of states, Svetlichny inequality is not violated when the $n-$tangle is less than $1/2$ for any even number of qubits. On the other hand, the maximal slice states always violate the Svetlichny inequality when $n-$tangle is nonzero, and the violation increases monotonically with tangle. Our work generalizes the relations between tangle and Svetlichny inequality violations previously derived for three qubits. - oai:arXiv.org:2409.10888v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - 10.1103/btbb-p514 - Phys. Rev. Research 7, 033289, Published 26 September, 2025 - Sanchit Srivastava, Shohini Ghose + Are Austad, Erik B\'edos, Jonas Eidesen, Nadia S. Larsen, Tron Omland - Universal adapters between quantum LDPC codes - https://arxiv.org/abs/2410.03628 - arXiv:2410.03628v3 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. This adapter is universal in the sense that it works regardless of the LDPC codes involved and the Paulis being measured. The construction achieves joint logical Pauli measurement of $t$ weight $O(d)$ operators using $O(td\log^2d)$ additional qubits and checks and $O(d)$ time. We also show for some geometrically-local codes in fixed $D\ge2$ dimensions that only $O(td)$ additional qubits and checks are required instead. By extending the adapter in the case $t=2$, we construct a toric code adapter that uses $O(d^2)$ additional qubits and checks to perform targeted logical CNOT gates on arbitrary LDPC codes via Dehn twists. To obtain some of these results, we develop a novel weaker form of graph edge expansion. - oai:arXiv.org:2410.03628v3 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Esha Swaroop, Tomas Jochym-O'Connor, Theodore J. Yoder + Heiko Georg Menzler, Suman Mondal, Fabian Heidrich-Meisner - Transient concurrence for copropagating entangled bosons and fermions - https://arxiv.org/abs/2410.12095 - arXiv:2410.12095v2 Announce Type: replace -Abstract: Transient dynamics of copropagating entangled bosons and fermions remains an unexplored aspect of quantum mechanics. We investigate how entanglement affects the spatiotemporal evolution of the particles using a modified version of the quantum shutter model. We derive a transient concurrence to characterize momentum-space entanglement, and show that it modulates the interference correlation of the joint probability density, allowing us to visualize the active regions where probabilistic bunching and antibunching phenomena emerge. Furthermore, we derive analytical expressions that reveal a direct connection between entanglement and the characteristic oscillations of the Hanbury-Brown and Twiss (HBT) effect, highlighting the modulation of the phenomenon by quantum concurrence. This work introduces a temporal indicator of entanglement for a system of two coherent copropagating modes establishing a direct relationship with HBT-type interference patterns, providing a theoretical framework to explore the manifestation of entanglement in transient regimes. - oai:arXiv.org:2410.12095v2 + 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 + physics.optics quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Miguel \'Angel Ter\'an, Roberto Romo, Gast\'on Garc\'ia-Calder\'on + Zhenzhong Xing, Hamim Mahmud Rivy, Vighnesh Natarajan, Aditya Milind Kolhatkar, Gillenhaal Beck, Karan K. Mehta - General, efficient, and robust Hamiltonian engineering - https://arxiv.org/abs/2410.19903 - arXiv:2410.19903v3 Announce Type: replace -Abstract: Implementing the time evolution under a desired target Hamiltonian is critical for various applications in quantum science. Due to the exponential increase in the number of parameters with system size and experimental imperfections, this task can be challenging in quantum many-body settings. - We introduce an efficient and robust scheme to engineer arbitrary local many-body Hamiltonians. To this end, our scheme applies single-qubit $\pi$ or $\pi/2$ pulses to an always-on system Hamiltonian, which we assume to be native to a given platform. These sequences are constructed by efficiently solving a linear program (LP) which minimizes the total evolution time. In this way, we can engineer target Hamiltonians that are only limited by the locality of the interactions in the system Hamiltonian. Based on average Hamiltonian theory and using robust composite pulses, we make our schemes robust against errors, including finite pulse time errors and various control errors. - To demonstrate the performance of our scheme, we provide numerical simulations. In particular, we solve the Hamiltonian engineering problem on a laptop for arbitrary two-local Hamiltonians on a 2D square lattice with $196$ qubits in only $60$ seconds. Moreover, we simulate the engineering of general Heisenberg Hamiltonians from Ising Hamiltonians using imperfect single-qubit pulses for smaller system sizes and achieve a fidelity exceeding $99.9\%$, which is orders of magnitude better than non-robust implementations. - oai:arXiv.org:2410.19903v3 + 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 + hep-th quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/9yxv-tdqr - PRX Quantum 6, 040346 (2025) - Pascal Ba{\ss}ler, Markus Heinrich, Martin Kliesch + Fri, 12 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + K. Hari, Subhajit Barman, Dawood Kothawala - Efficient explicit circuit for quantum state preparation of piecewise continuous functions - https://arxiv.org/abs/2411.01131 - arXiv:2411.01131v4 Announce Type: replace -Abstract: Efficiently uploading data into quantum states is essential for many quantum algorithms to achieve advantage across various applications. In this paper, we address this challenge by developing a method to upload a polynomial function $f(x)$ on the interval $x \in [-1,1]$ into a pure quantum state consisting of qubits, where a discretized $f(x)$ is the amplitude of this state. The preparation cost has $\mathcal{O}(n\log n)$ scaling in the number of qubits $n$ and linear scaling with the degree of the polynomial $Q$. This efficiency allows the preparation of states whose amplitudes correspond to high-degree polynomials (up to $10^4$), enabling accurate approximation of functions that admit efficient polynomial series representations and whose amplitude profiles are not extremely localized. We provide a fully explicit circuit realization, based on four real polynomials that meet specific parity and boundedness conditions. We extend this construction to cover piece-wise polynomial functions, a case not previously addressed explicitly in the literature, the algorithm scaling linearly with the number of piecewise parts. Our method achieves efficient quantum circuit implementation and we present detailed gate counting and resource analysis. - oai:arXiv.org:2411.01131v4 + 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 + cond-mat.mes-hall quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace + Fri, 12 Dec 2025 00:00:00 -0500 + cross http://creativecommons.org/licenses/by/4.0/ - Nikita Guseynov, Nana Liu + Filippo Gaggioli, Pierre-Antoine Graham, Liang Fu - Machine Learning for Arbitrary Single-Qubit Rotations on an Embedded Device - https://arxiv.org/abs/2411.13037 - arXiv:2411.13037v2 Announce Type: replace -Abstract: Here we present a technique for using machine learning (ML) for single-qubit gate synthesis on field programmable logic for a superconducting transmon-based quantum computer based on simulated studies. Our approach is multi-stage. We first bootstrap a model based on simulation with access to the full statevector for measuring gate fidelity. We next present an algorithm, named adapted randomized benchmarking (ARB), for fine-tuning the gate on hardware based on measurements of the devices. We also present techniques for deploying the model on programmable devices with care to reduce the required resources. While the techniques here are applied to a transmon-based computer, many of them are portable to other architectures. - oai:arXiv.org:2411.13037v2 + 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 quant-ph - cs.ET - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Matt Wilson + + + 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 + quant-ph + cs.IT + math.IT + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1007/s42484-024-00214-8 - Madhav Narayan Bhat, Marco Russo, Luca P. Carloni, Giuseppe Di Guglielmo, Farah Fahim, Andy C. Y. Li, Gabriel N. Perdue + http://creativecommons.org/licenses/by/4.0/ + Diego Forlivesi, Lorenzo Valentini, Marco Chiani - Continuous-variable quantum communication - https://arxiv.org/abs/2501.12801 - arXiv:2501.12801v2 Announce Type: replace -Abstract: Tremendous progress in experimental quantum optics during the past decades enabled the advent of quantum technologies, one of which is quantum communication. Aimed at novel methods for more secure or efficient information transfer, quantum communication has developed into an active field of research and proceeds toward full-scale implementations and industrialization. Continuous-variable methods of multi-photon quantum state preparation, manipulation, and coherent detection, as well as the respective theoretical tools of phase-space quantum optics, offer the possibility to make quantum communication efficient, applicable and accessible, thus boosting the development of the field. We review the methodology, techniques and protocols of continuous-variable quantum communication, from the first theoretical ideas, through milestone implementations, to the recent developments, covering quantum key distribution as well as other quantum communication schemes, suggested on the basis of continuous-variable states and measurements. - oai:arXiv.org:2501.12801v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Vladyslav C. Usenko, Antonio Ac\'in, Romain All\'eaume, Ulrik L. Andersen, Eleni Diamanti, Tobias Gehring, Adnan A. E. Hajomer, Florian Kanitschar, Christoph Pacher, Stefano Pirandola, Valerio Pruneri + http://creativecommons.org/licenses/by/4.0/ + Sanam Khan, R. Jehadeesan, Sibasish Ghosh - Temperature and non-Markovian parameter estimation in quantum Brownian motion - https://arxiv.org/abs/2504.08529 - arXiv:2504.08529v3 Announce Type: replace -Abstract: We investigate a quantum metrological protocol operating in a non-Markovian environment by employing the quantum Brownian motion (QBM) model, in which the system is linearly coupled to a reservoir of harmonic oscillators. Specifically, we use a position-momentum (PM) correlated Gaussian state as a probe to examine how memory effects influence the evolution of the system's covariance matrix in the weak coupling regime under both high- and low-temperature conditions. To confirm the presence of non-Markovian behavior, we apply two well-established non-Markovianity quantifiers. Furthermore, we estimate both the channel's sample temperature and its non-Markovianity witness parameter. Our results demonstrate that non-Markovianity and PM correlations can jointly be valuable resources to enhance metrological performance. - oai:arXiv.org:2504.08529v3 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + math-ph + math.MP + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/c87r-22mn - Jo\~ao C. P. Porto, Carlos H. S. Vieira, Irismar G. da Paz, Pedro R. Dieguez, Lucas S. Marinho + http://creativecommons.org/licenses/by/4.0/ + Shrigyan Brahmachari, Roberto Rubboli, Marco Tomamichel - Entangled Subspaces through Algebraic Geometry - https://arxiv.org/abs/2504.11525 - arXiv:2504.11525v2 Announce Type: replace -Abstract: We propose an algebraic geometry-inspired approach for constructing entangled subspaces within the Hilbert space of a multipartite quantum system. Specifically, our method employs a modified Veronese embedding, restricted to the conic, to define subspaces within the symmetric part of the Hilbert space. By utilizing this technique, we construct the minimal-dimensional, non-orthogonal yet Unextendible Product Basis (nUPB), enabling the decomposition of the multipartite Hilbert space into a two-dimensional subspace, complemented by a Genuinely Entangled Subspace (GES) and a maximal-dimensional Completely Entangled Subspace (CES). In multiqudit systems, we determine the maximum achievable dimension of a symmetric GES and demonstrate its realization through this construction. Furthermore, we systematically investigate the transition from the conventional Veronese embedding to the modified one by imposing various constraints on the affine coordinates, which, in turn, increases the CES dimension while reducing that of the GES. - oai:arXiv.org:2504.11525v2 + 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 quant-ph + hep-th math-ph - math.AG math.MP - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Masoud Gharahi, Stefano Mancini + Takayuki Hori - Benchmarking data encoding methods in Quantum Machine Learning - https://arxiv.org/abs/2505.14295 - arXiv:2505.14295v2 Announce Type: replace -Abstract: Data encoding plays a fundamental and distinctive role in Quantum Machine Learning (QML). While classical approaches process data directly as vectors, QML may require transforming classical data into quantum states through encoding circuits, known as quantum feature maps or quantum embeddings. This step leverages the inherently high-dimensional and non-linear nature of Hilbert space, enabling more efficient data separation in complex feature spaces that may be inaccessible to classical methods. This encoding part significantly affects the performance of the QML model, so it is important to choose the right encoding method for the dataset to be encoded. However, this choice is generally arbitrary, since there is no "universal" rule for knowing which encoding to choose based on a specific set of data. There are currently a variety of encoding methods using different quantum logic gates. We studied the most commonly used types of encoding methods and benchmarked them using different datasets. - oai:arXiv.org:2505.14295v2 + 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 quant-ph - cs.AI - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Orlane Zang, Gr\'egoire Barru\'e, Tony Quertier + Esha Swaroop, Tomas Jochym-O'Connor, Theodore J. Yoder - Hierarchic superradiant phases in anisotropic Dicke model - https://arxiv.org/abs/2505.21169 - arXiv:2505.21169v3 Announce Type: replace -Abstract: We revisit the phase diagram of an anisotropic Dicke model by revealing the non-analyticity induced by underlying exceptional points. We find that, from a dynamical perspective, the conventional superradiant phase can be further separated into three regions, in which the systems are characterized by different effective Hamiltonians, including the harmonic oscillator, the inverted harmonic oscillator, and their respective counterparts. We employ the Loschmidt echo to characterize different quantum phases by analyzing the quench dynamics of a trivial initial state. Numerical simulations for finite systems confirm our predictions about the existence of hierarchic superradiant phases. - oai:arXiv.org:2505.21169v3 + 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 quant-ph - cond-mat.str-el - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - D. K. He, Z. Song + 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 - Giant atom with disorders: Effects from imperfect couplings - https://arxiv.org/abs/2506.03628 - arXiv:2506.03628v3 Announce Type: replace -Abstract: The study of giant atoms goes beyond the local interaction paradigm in the conventional quantum optics, and predicts novel phenomena, such as oscillating bound states in the continuum (BICs) and decoherence-free interaction (DFI) that do not exist in small atoms, for some particular parameter settings of coupling positions and strengths. However, in the realistic experiments to implement giant-atom systems, there is always some level of disorder both in coupling positions and strengths. In this work, we investigate the effects of disorder on the phenomena related to giant atoms. We find that the giant-atom related phenomena are robust to both disorders of coupling positions and strengths in the Markovian regime, but more sensitive to the disorder of coupling positions in the non-Markovian regime. Our work shows that, to observe the non-Markovian phenomenon such as (oscillating) BICs in giant-atom systems, more precision is needed to control the disorder of coupling positions than that of the coupling strengths in the experiments. - oai:arXiv.org:2506.03628v3 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/1px2-2db4 - Muming Han, Lingzhen Guo + Xiao-Hui Ni, Yu-Sen Wu, Bin-Bin Cai, Wen-Min Li, Su-Juan Qin, Fei Gao - Inline Quantum Measurements with SNSPDs Coupled to Photonic Bound States - https://arxiv.org/abs/2506.07029 - arXiv:2506.07029v2 Announce Type: replace -Abstract: We report the realization of inline quantum measurements with waveguide-integrated superconducting nanowire single-photon detectors (SNSPDs). To suppress parasitic scattering at detector terminations, while ensuring compatibility with standard photonic substrates and cryogenic operation, we developed a photonic bound states in the continuum (BIC) platform based on etchless polymer waveguides. We show BIC-coupled inline detectors with on-chip efficiency exceeding 80%, recovery time of less than 2 ns, and intrinsic jitter of less than 70 ps. As a proof of principle, we implement Hanbury Brown and Twiss interferometry and photon number resolution with two collinear detectors within a footprint of $60 \cdot 6$ $\mu m^2$. The concept of inline quantum measurements could be further developed to support more complex circuit functionalities, such as higher-order correlation measurements, quantum state tomography, and multi-photon subtraction, within a compact architecture. - oai:arXiv.org:2506.07029v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Filippo Martinelli, Anton N. Vetlugin, Shuyu Dong, Darren M. Z. Koh, Mariia Sidorova, Christian Kurtsiefer, Cesare Soci + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Newton Loebens - Certifying asymmetry in the configuration of three qubits - https://arxiv.org/abs/2506.09939 - arXiv:2506.09939v2 Announce Type: replace -Abstract: Symmetry restrictions limit the types of tasks that can be achieved with a given set of quantum states. Therefore, any breaking of these symmetries could potentially be exploited as a resource for quantum communication. Here we demonstrate this operationally by certifying asymmetry in the configuration of the Bloch vectors of a set of three unknown qubit states within the dimensionally bounded prepare-and-measure scenario. To do this, we construct a linear witness from three simpler witnesses as building blocks, each featuring, along with two binary measurement settings, three preparations; two of them are associated with the certification task, while the third one serves as an auxiliary. The final witness is chosen to self-test some target configuration. We numerically derive a bound $Q_{\text{mirror}}$ for any mirror-symmetric configuration, thereby certifying asymmetry if this bound is exceeded (e.g. experimentally) for the unknown qubit configuration. We also consider the gap $(Q_{\text{max}}-Q_{\text{mirror}})$ between the analytically derived overall quantum maximum $Q_{\text{max}}$ and the mirror-symmetric bound, and use it as a quantifier of asymmetry in the target configuration. Numerical optimization shows that the most asymmetric configuration then forms a right scalene triangle on the unit Bloch sphere. Finally, we implement our protocol on a public quantum processor, where a clear violation of the mirror-symmetric bound certifies asymmetry in the configuration of our experimental triple of qubit states. - oai:arXiv.org:2506.09939v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cs.IT + math-ph + math.IT + math.MP + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1088/1367-2630/ae1ce3 - New J. Phys. 27, 124501 (2025) - Abdelmalek Taoutioui, G\'abor Dr\'otos, Tam\'as V\'ertesi + Bartosz Regula, Ludovico Lami, Nilanjana Datta - Higher-Order Adiabatic Elimination in Atom-Cavity Systems and Its Impact on Spin-Squeezing Generation - https://arxiv.org/abs/2506.22383 - arXiv:2506.22383v3 Announce Type: replace -Abstract: Spin-squeezed states are metrologically useful quantum states where entanglement allows for enhanced sensing with respect to the standard quantum limit. Key challenges include the efficient preparation of spin-squeezed states and the scalability of estimation precision with the number $N$ of probes. Recently, in the context of the generation of spin-squeezed states via coupling of three-level atoms to an optical cavity, it was shown that increasing the atom-cavity coupling can be detrimental to spin squeezing generation, an effect that is not captured by the standard second-order adiabatic cavity removal approximation. We describe adiabatic elimination techniques to derive an effective Lindblad master equation up to third order for the atomic degrees of freedom. Numerical simulations show that the spin squeezing scalability loss is correctly reproduced by the reduced open system dynamics, highlighting the role of higher-order contributions. Furthermore, we conjecture an extension beyond leading order of the adiabatic elimination technique to the case of conditional dynamics under quantum non-demolition continuous measurement and fast cavity loss, whose reliability is again confirmed by numerical simulation of the dynamics and the corresponding behavior of spin squeezing as a function of $N$. - oai:arXiv.org:2506.22383v3 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.dis-nn + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Stefano Giaccari, Giulia Dellea, Marco G. Genoni, Gianluca Bertaina + 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 - Photon condensation from thermal sources and the limits of heat engines - https://arxiv.org/abs/2507.19128 - arXiv:2507.19128v2 Announce Type: replace -Abstract: The trapping and cooling of photon gases in microcavities has been used to create Bose-Einstein condensates. We investigate the conditions required for condensation in dye-filled microcavities, with photon populations created either by driving a transition of the dye, or by coupling the cavity modes to a thermal photon reservoir such as sunlight. We find that the threshold pump temperature, above which condensation appears, is determined by the second law of thermodynamics. The minimum achievable threshold is that of a reversible three-level heat engine, which we show arises in the dye-pumped case, and for pumping of the modes of a two-level cavity. For a many-level cavity condensation occurs at a similar but higher temperature. Our results show that photon condensates can be produced by pumping with incoherent thermal sources, opening possibilities for coherent light generation, energy harvesting, and experimental studies of quantum heat engines. - oai:arXiv.org:2507.19128v2 + 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 quant-ph - cond-mat.quant-gas - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Luisa Toledo Tude, Emily Haughton, Paul R. Eastham + Mingyu Huang, Ji Guan, Wang Fang, Mingsheng Ying - Structured quantum learning via em algorithm for Boltzmann machines - https://arxiv.org/abs/2507.21569 - arXiv:2507.21569v2 Announce Type: replace -Abstract: Quantum Boltzmann machines (QBMs) are generative models with potential advantages in quantum machine learning, yet their training is fundamentally limited by the barren plateau problem, where gradients vanish exponentially with system size. We introduce a quantum version of the em algorithm, an information-geometric generalization of the classical Expectation-Maximization method, which circumvents gradient-based optimization on non-convex functions. Implemented on a semi-quantum restricted Boltzmann machine (sqRBM) -- a hybrid architecture with quantum effects confined to the hidden layer -- our method achieves stable learning and outperforms gradient descent on multiple benchmark datasets. These results establish a structured and scalable alternative to gradient-based training in QML, offering a pathway to mitigate barren plateaus and enhance quantum generative modeling. - oai:arXiv.org:2507.21569v2 + 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 quant-ph - cs.LG - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Takeshi Kimura, Kohtaro Kato, Masahito Hayashi + Alan Duriez, Pamela C. Carvalho, Marco Antonio Barroca, Federico Zipoli, Ben Jaderberg, Rodrigo Neumann Barros Ferreira, Kunal Sharma, Antonio Mezzacapo, Benjamin Wunsch, Mathias Steiner - Quantum coherence and negative quasi probabilities in a contextual three-path interferometer - https://arxiv.org/abs/2507.22323 - arXiv:2507.22323v2 Announce Type: replace -Abstract: Basic quantum effects are often illustrated using single particle interferences in two-path interferometers. A wider range of non-classical phenomena can be illustrated using three-path interferometers, but the increased complexity of quantum statistics in a three-dimensional Hilbert space makes it difficult to identify a representative set of observable properties that could be used to characterize specific phenomena. Here, I propose a characterization of pure states based on a five-stage interferometer recently introduced to demonstrate the relation between different measurement contexts (Optica Quantum 1, 63 (2023)). It is shown that the orthogonality relations between the states representing the different measurement contexts can be used to classify pure states within the three-dimensional Hilbert space according to the non-classical correlations between different contexts expressed by negative Kirkwood-Dirac distributions. - oai:arXiv.org:2507.22323v2 + 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 quant-ph - physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + cs.IT + math.IT + math.OA + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Holger F. Hofmann + Owen Ekblad - Stoquasticity is not enough: towards a sharper diagnostic for Quantum Monte Carlo simulability - https://arxiv.org/abs/2508.14382 - arXiv:2508.14382v2 Announce Type: replace -Abstract: Quantum Monte Carlo (QMC) methods are powerful tools for simulating quantum many-body systems, yet their applicability is limited by the infamous sign problem. We approach this challenge through the lens of Vanishing Geometric Phases (VGP) \cite{Hen_2021}, introducing it as a `geometric' criterion for diagnosing QMC simulability. We characterize the class of VGP Hamiltonians, and analyze the complexity of recognizing this class, identifying both hard and efficiently identifiable cases. We further highlight the practical advantage of the VGP criterion by exhibiting specific Hamiltonians that are readily identified as sign-problem-free through VGP, yet whose stoquasticity is difficult to ascertain. These examples underscore the efficiency and sharpness of VGP as a diagnostic tool compared to stoquasticity-based heuristics. Beyond classification, we propose a family of VGP-inspired diagnostics that serve as quantitative indicators of sign problem severity. While exact evaluation of these quantities is generically intractable, we demonstrate their mathematical power in performing scaling analysis for the average sign under unitary transformations. Our results provide both a conceptual foundation and practical tools for understanding and mitigating the sign problem. - oai:arXiv.org:2508.14382v2 + 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 quant-ph - cond-mat.stat-mech - physics.comp-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Arman Babakhani, Armen Karakashian + Andrea Mammola, Quentin Schaeverbeke, Giuseppe Di Molfetta - Magnetic noise in macroscopic quantum spatial superposition induced by inverted harmonic oscillator potential - https://arxiv.org/abs/2509.02670 - arXiv:2509.02670v2 Announce Type: replace -Abstract: We investigate a Stern-Gerlach type matter-wave interferometer where an inhomogeneous magnetic field couples to an embedded spin in a nanoparticle to create spatial superpositions. Employing a sequence of harmonic and inverted harmonic oscillator potentials created by external magnetic fields, we aim to enhance the one-dimensional superposition of a nanodiamond with mass $\sim 10^{-15}$ kg to $\sim 1 \mu$m. However, random fluctuations of the magnetic field stochastically perturbs the interferometer paths and induce dephasing. We quantitatively estimate the susceptibility of the interferometer to white noise arising from magnetic-field fluctuations. Constraining the dephasing rate \(\Gamma\) to be low enough that the final coherence \(e^{-\Gamma \tau}\leq 0.1\) (where \(\tau\) is the experimental time duration), we obtain the following bounds on the noise to signal ratios: $\delta \eta_\text{IHP}/\eta_\text{IHP}\lesssim 10^{-13}$, where $\eta_\text{IHP}$ is the magnetic field curvature that gives rise to the inverted harmonic potential, and $\delta \eta_\text{HP}/\eta_\text{HP}\lesssim 10^{-6}$, where $\eta_\text{HP}$ is the linear magnetic field gradient that gives rise to the harmonic potential. For such tiny fluctuations, we demonstrate that the Humpty-Dumpty problem arising from a mismatch in position and momentum does not cause a loss in contrast of the interferometer. Further, we show that constraining the dephasing rate leads to stricter bounds on the noise parameters than enforcing a contrast threshold, indicating that good dephasing control ensures high interferometric contrast. - oai:arXiv.org:2509.02670v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Sneha Narasimha Moorthy, Anupam Mazumdar + Lei Zhang, Jizhe Lai, Xian Wu, Xin Wang - Measuring Multiparticle Indistinguishability with the Generalized Bunching Probability - https://arxiv.org/abs/2509.04550 - arXiv:2509.04550v4 Announce Type: replace -Abstract: The indistinguishability of many bosons undergoing passive linear transformations followed by number basis measurements is fully characterized by the visible state of the bosons. However, measuring all the parameters in the visible state is experimentally demanding. In this work, we seek to perform partial characterization of the visible state by measuring properties of it that are available after randomization. First we study the case where the occupied visible modes are randomly permuted, and second we study the case where Haar random linear optical unitaries are applied. In each case, we find that the generalized bunching probability -- which is the probability that all the input bosons arrive in a given subset of the output modes -- obeys monotonicity with respect to some partial order of distinguishability of the input bosons. As an intermediate result, we show that Lieb's permanental-dominance conjecture for immanants is equivalent to the following statement: for states that are invariant under permutations of the occupied visible modes, the generalized bunching probability is maximized when the bosons are perfectly indistinguishable. We also prove that a consequence of the monotonicity of the generalized bunching probability after Haar averaging is that this average is maximized when the bosons are perfectly indistinguishable. Finally, we discuss applications of our results to thermometry of cold-atom systems. - oai:arXiv.org:2509.04550v4 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cs.DC + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Shawn Geller, Emanuel Knill + Riccardo Mengoni, Walter Nadalin, Mathys Rennela, Jimmy Rotureau, Tom Darras, Julien Laurat, Eleni Diamanti, Ioannis Lavdas - Diffraction by Circular and Triangular Apertures as a Diagnostic Tool of Twisted Matter Waves - https://arxiv.org/abs/2510.00826 - arXiv:2510.00826v3 Announce Type: replace -Abstract: We study diffraction of twisted matter waves (electrons and light ions carrying orbital angular momentum $\ell/\hbar=0,\pm1,\pm2,\ldots$ by circular and triangular apertures. Within the scalar Kirchhoff-Fresnel framework, circular apertures preserve cylindrical symmetry and produce ringlike far-field profiles whose radii and widths depend on $|\ell|$ but are insensitive to its sign. In contrast, equilateral triangles break axial symmetry and yield structured patterns that encode both the magnitude and the sign of $\ell$. A transparent Fraunhofer mapping links detector coordinates to the Fourier plane, explaining the $(|\ell|+1)$-lobe rule and the sign-dependent rotation of the pattern. We validate these results for both ideal Bessel beams and localized Laguerre-Gaussian packets, and we cross-check them by split-step Fourier propagation of the time-dependent Schr"odinger equation. From these analyses we extract practical design rules (Fraunhofer distance, lattice pitch, detector sampling) relevant to OAM diagnostics with moderately relativistic electrons with $E_{\rm kin}\sim0.1$ to $5$ MeV and light ions with $E_{\rm kin}\sim0.1$ to $1$ MeV/u. Our results establish triangular diffraction as a simple, passive, and robust method for reading out the OAM content of structured quantum beams. - oai:arXiv.org:2510.00826v3 + 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 quant-ph - hep-ph - physics.acc-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/z2rs-2ryl - Maksim Maksimov, Nikita Borodin, Daria Kargina, Dmitry Naumov, Dmitry Karlovets + http://creativecommons.org/licenses/by/4.0/ + Issam Ibnouhsein - Good quantum codes with addressable and parallelizable transversal non-Clifford gates - https://arxiv.org/abs/2510.19809 - arXiv:2510.19809v2 Announce Type: replace -Abstract: In this work, we prove that for any $m>1$, there exists a family of good qudit quantum codes supporting transversal logical $\mathsf{C}^{m-1}\mathsf{Z}$ gates that can address specified logical qudits and be largely executed in parallel. Building on the family of good quantum error-correcting codes presented in He et al. (2025), which support addressable and transversal logical $\mathsf{CCZ}$ gates, we extend their framework and show how to perform large sets of gates in parallel. The construction relies on the classical algebraic geometry codes of Stichtenoth (IEEE Trans. Inf. Theory, 2006). Our results lead to a substantial reduction in the depth overhead of multi-control-$Z$ circuits. In particular, we show that the minimal depth of any logical $\mathsf{C}^{m-1}\mathsf{Z}$ circuit involving qudits from $m$ distinct code blocks is upper bounded by $O(k^{m-1})$, where $k$ is the code dimension. While this overhead is optimal for dense $\mathsf{C}^{m-1}\mathsf{Z}$ circuits, for sparse circuits we discuss how the depth overhead can be significantly reduced by exploiting the structure of the quantum code. - oai:arXiv.org:2510.19809v2 + 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 quant-ph - cs.IT - math.IT - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Virgile Gu\'emard + 10.1088/2058-9565/ae2885 + Danilo Triggiani, Cosmo Lupo - The three kinds of three-qubit entanglement - https://arxiv.org/abs/2511.07617 - arXiv:2511.07617v2 Announce Type: replace -Abstract: We construct an important missing piece in the entanglement theory of pure three-qubit states, which is a polynomial measure of W-entanglement, working in parallel to the three-tangle, which is a polynomial measure of GHZ-entanglement, and to the bipartite concurrence, which is a polynomial measure of bipartite entanglement. We also show that these entanglement measures are ordered, the bipartite measure is larger than the W measure, which is larger than the GHZ measure. It is meaningful then to consider these three types of three-qubit entanglement, which are also ordered, bipartite is weaker than W, which is weaker than GHZ, in parallel to the order of the three equivalence classes of entangled three-qubit states. - oai:arXiv.org:2511.07617v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cs.AI + Fri, 12 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Szil\'ard Szalay + http://creativecommons.org/licenses/by/4.0/ + David Kremer, Ali Javadi-Abhari, Priyanka Mukhopadhyay - Quantum resource degradation theory within the framework of observational entropy decomposition - https://arxiv.org/abs/2511.22350 - arXiv:2511.22350v2 Announce Type: replace -Abstract: We introduce a theory of quantum resource degradation grounded in a decomposition of observational entropy, which partitions the total resource into inter-block coherence ($\mathcal{C}_{\text{rel}}$) and intra-block noise ($\mathcal{D}_{\text{rel}}$). Under free operations, the total quantum resource is transformed into classical noise while its overall quantity remains conserved. We demonstrate that the metric $\eta$ functions as a diagnostic indicator, providing a new lens on optimization stagnation, particularly the barren plateau phenomenon (BPP) in variational quantum algorithms (VQAs). We substantiate this framework through rigorous mathematical analysis and numerical simulations, and we explore how these channels can be physically implemented in real quantum systems. Our approach offers a unified viewpoint on quantum thermalization, measurement-induced disturbance, and the degradation of quantum advantage in practical devices, while also improving optimization strategies for current and near-term noisy quantum hardware. - oai:arXiv.org:2511.22350v2 + 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 quant-ph math-ph math.MP - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiang Zhou + Einar Gabbassov - Data-Driven Learnability Transition of Measurement-Induced Entanglement - https://arxiv.org/abs/2512.01317 - arXiv:2512.01317v2 Announce Type: replace -Abstract: Measurement-induced entanglement (MIE) captures how local measurements generate long-range quantum correlations and drive dynamical phase transitions in many-body systems. Yet estimating MIE experimentally remains challenging: direct evaluation requires extensive post-selection over measurement outcomes, raising the question of whether MIE is accessible with only polynomial resources. We address this challenge by reframing MIE detection as a data-driven learning problem that assumes no prior knowledge of state preparation. Using measurement records alone, we train a neural network in a self-supervised manner to predict the uncertainty metric for MIE--the gap between upper and lower bounds of the average post-measurement bipartite entanglement. Applied to random circuits with one-dimensional all-to-all connectivity and two-dimensional nearest-neighbor coupling, our method reveals a learnability transition with increasing circuit depth: below a threshold, the uncertainty is small and decreases with polynomial measurement data and model parameters, while above it the uncertainty remains large despite increasing resources. We further verify this transition experimentally on current noisy quantum devices, demonstrating its robustness to realistic noise. These results highlight the power of data-driven approaches for learning MIE and delineate the practical limits of its classical learnability. - oai:arXiv.org:2512.01317v2 + 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 quant-ph - cond-mat.dis-nn - cs.AI - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Dongheng Qian, Jing Wang + Xudong Zhang, Zhaoyu Sun, Bin Guo - Quantum hypergraph states: a review - https://arxiv.org/abs/2512.02955 - arXiv:2512.02955v2 Announce Type: replace -Abstract: Quantum hypergraph states emerged in the literature as a generalization of graph states, and since then, considerable progress has been made toward implementing this class of genuine multipartite entangled states for quantum information and computation. Here, we review the definition of hypergraph states and their main applications so far, both in discrete-variable and continuous-variable quantum information. - oai:arXiv.org:2512.02955v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cs.SY + eess.SY + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Vin\'icius Salem + Zihao Ren, Daniel Quevedo, Salah Sukkarieh, Guodong Shi - F2: Offline Reinforcement Learning for Hamiltonian Simulation via Free-Fermionic Subroutine Compilation - https://arxiv.org/abs/2512.08023 - arXiv:2512.08023v2 Announce Type: replace -Abstract: Compiling shallow and accurate quantum circuits for Hamiltonian simulation remains challenging due to hardware constraints and the combinatorial complexity of minimizing gate count and circuit depth. Existing optimization method pipelines rely on hand-engineered classical heuristics, which cannot learn input-dependent structure and therefore miss substantial opportunities for circuit reduction. - We introduce F2, an offline reinforcement learning framework that exploits free-fermionic structure to efficiently compile Trotter-based Hamiltonian simulation circuits. F2 provides (i) a reinforcement-learning environment over classically simulatable free-fermionic subroutines, (ii) architectural and objective-level inductive biases that stabilize long-horizon value learning, and (iii) a reversible synthetic-trajectory generation mechanism that consistently yields abundant, guaranteed-successful offline data. - Across benchmarks spanning lattice models, protein fragments, and crystalline materials (12-222 qubits), F2 reduces gate count by 47% and depth by 38% on average relative to strong baselines (Qiskit, Cirq/OpenFermion) while maintaining average errors of 10^(-7). These results show that aligning deep reinforcement learning with the algebraic structure of quantum dynamics enables substantial improvements in circuit synthesis, suggesting a promising direction for scalable, learning-based quantum compilation - oai:arXiv.org:2512.08023v2 + 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 quant-ph - cond-mat.mtrl-sci - Thu, 11 Dec 2025 00:00:00 -0500 + physics.bio-ph + physics.chem-ph + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Ethan Decker, Christopher Watson, Junyu Zhou, Yuhao Liu, Chenxu Liu, Ang Li, Gushu Li, Samuel Stein + Daniele Loco, Kisa Barkemeyer, Andre R. R. Carvalho, Jean-Philip Piquemal High-OAM Deep Ultraviolet Twisted Light Generation for RF-Photoinjector Applications https://arxiv.org/abs/2512.08442 - arXiv:2512.08442v2 Announce Type: replace + 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:2512.08442v2 + oai:arXiv.org:2512.08442v3 quant-ph physics.acc-ph physics.optics - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 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 - Quantum Brownian Motion as a Classical Stochastic Process in Phase Space - https://arxiv.org/abs/2512.08641 - arXiv:2512.08641v2 Announce Type: replace -Abstract: We establish that the exact quantum dynamics of a Brownian particle in the Caldeira-Leggett model can be mapped, at any temperature, onto a classical, non-Markovian stochastic process in phase space. Starting from a correlated thermal equilibrium state between the particle and bath, we prove that this correspondence is exact for quadratic potentials under arbitrary quantum state preparations of the particle itself. For more general, smooth potentials, we identify and exploit a natural small parameter: the density matrix becomes strongly quasidiagonal in the coordinate representation, with its off-diagonal width shrinking as the bath's spectral cutoff increases, providing a controlled parameter for accurate approximation. The framework is fully general: arbitrary initial quantum states-including highly non-classical superpositions-are incorporated via their Wigner functions, which serve as statistical weights for trajectory ensembles. Furthermore, the formalism naturally accommodates external manipulations and measurements modeled by preparation functions acting at arbitrary times, enabling the simulation of complex driven-dissipative quantum protocols. - oai:arXiv.org:2512.08641v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + cond-mat.mes-hall + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Dmitriy Kondaurov, Evgeny Polyakov + 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 - A Unified Framework for Optimizing Uniformly Controlled Structures in Quantum Circuits - https://arxiv.org/abs/2512.08675 - arXiv:2512.08675v2 Announce Type: replace -Abstract: Quantum unitaries of the form $\Sigma_{c}\ket{c}\bra{c}\otimes U_{c}$ are ubiquitous in quantum algorithms. This class encompasses not only standard uniformly controlled gates (UCGs) but also a wide range of circuits with uniformly controlled structures. However, their circuit-depth and gate-count complexities have not been systematically analyzed within a unified framework. In this work, we study the general decomposition problem for UCG and UCG-like structure. We then introduce the restricted Uniformly Controlled Gates (rUCGs) as a unified algebraic model, defined by a 2-divisible Abelian group that models the controlled gate set. This model captures uniformly controlled rotations, multi-qubit uniformly controlled gates, and diagonal unitaries. Furthermore, this model also naturally incorporates k-sparse version (k-rUCGs), where only a subset of control qubits participate in each multi-qubit gate. Building on this algebraic model, we develop a general framework. For an n-control rUCG, the framework reduce the gate complexity from ${O(n2^n)}$ to ${O(2^n})$ and the circuit depth from ${O(2^n\log n)}$ to ${O(2^n\log n/n)}$. The framework further provides systematic size and depth bounds for k-rUCGs by exploiting sparsity in the control space, with same optimization coefficient as rUCG, respectively. Empirical evaluations on representative QAOA circuits confirm reductions in depth and size, which highlight that the rUCG model and its associated decomposition framework unify circuits previously considered structurally distinct under a single, asymptotically optimal synthesis paradigm. - oai:arXiv.org:2512.08675v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Chengzhuo Xu, Xiao Chen, Xi Li, Zhihao Liu, Zhigang Li + Karl Svozil - Autonomous multi-ion optical clock with on-chip integrated photonic light delivery - https://arxiv.org/abs/2512.08921 - arXiv:2512.08921v2 Announce Type: replace -Abstract: Integrated photonics in trapped-ion systems are critical for the realization of applications such as portable optical atomic clocks and scalable quantum computers. However, system-level integration of all required functionalities remains a key challenge. In this work, we demonstrate an autonomously operating optical clock having a short-term frequency instability of $3.14(5)\times 10^{-14} / \sqrt{\tau}$ using an ensemble of four $^{171}\textrm{Yb}^{+}$ ions trapped in a multi-site surface-electrode trap at room temperature. All clock operations are performed with light delivered via on-chip waveguides. We showcase the system's resilience through sustained, autonomous operation featuring automated ion shuttling and reloading to mitigate ion loss during interleaved clock measurements. This work paves the way beyond component-level functionality to establish a viable and robust architecture for the next generation of portable, multi-ion quantum sensors and computers. - oai:arXiv.org:2512.08921v2 + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + gr-qc + hep-th + math-ph + math.MP + Fri, 12 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Tharon D. Morrison, Joonhyuk Kwon, Matthew A. Delaney, David R. Leibrandt, Daniel Stick, Hayden J. McGuinness - - - Equiangular lines via matrix projection - https://arxiv.org/abs/2110.15842 - arXiv:2110.15842v5 Announce Type: replace-cross -Abstract: In 1973, Lemmens and Seidel posed the problem of determining the maximum number of equiangular lines in $\mathbb{R}^r$ with angle $\arccos(\alpha)$ and gave a partial answer in the regime $r \leq 1/\alpha^2 - 2$. At the other extreme where $r$ is at least exponential in $1/\alpha$, recent breakthroughs have led to an almost complete resolution of this problem. In this paper, we introduce a new method for obtaining upper bounds which unifies and improves upon previous approaches, thereby yielding bounds which bridge the gap between the aforementioned regimes and are best possible either exactly or up to a small multiplicative constant. Our approach relies on orthogonal projection of matrices with respect to the Frobenius inner product and as a byproduct, it yields the first extension of the Alon-Boppana theorem to dense graphs, with equality for strongly regular graphs corresponding to $\binom{r+1}{2}$ equiangular lines in $\mathbb{R}^r$. Applications of our method in the complex setting will be discussed as well. - oai:arXiv.org:2110.15842v5 - math.CO - cs.IT - math.IT - math.MG - quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Igor Balla + Sridhar Tayur - Emergent metric from wavelet-transformed quantum field theory - https://arxiv.org/abs/2504.06698 - arXiv:2504.06698v3 Announce Type: replace-cross -Abstract: We introduce a method of reverse holography by which a bulk metric is shown to arise from locally computable multiscale correlations of a boundary quantum field theory (QFT). The metric is obtained from the Petz-R\'enyi mutual information defined with input correlations computed from the continuous wavelet transform. The method is applicable to a variety of boundary QFTs that need not be conformal field theories (CFTs). For thermal free scalar and Dirac field theories the resulting bulk metric is that of (asymmetrically) warped anti-de Sitter (AdS) space. For massless, ground state CFTs the geometry simply reduces to AdS space. We show that certain parameters of the geometry can be tuned by changing the shape of the wavelet function. - oai:arXiv.org:2504.06698v3 - hep-th + 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 + math-ph + math.MP quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - \v{S}imon Vedl, Daniel J. George, Fil Simovic, Dominic G. Lewis, Nicholas Funai, Achim Kempf, Nicolas C. Menicucci, Gavin K. Brennen + 10.1103/PhysRevB.103.075441 + Phys. Rev. B 103, 075441 (2021) + Vivek M. Vyas, Dibyendu Roy - From spin to pseudospin symmetry: The origin of magic numbers in nuclear structure - https://arxiv.org/abs/2504.09148 - arXiv:2504.09148v2 Announce Type: replace-cross -Abstract: Magic numbers lie at the heart of nuclear structure, reflecting enhanced stability in nuclei with closed shells. While the emergence of magic numbers beyond 20 is commonly attributed to strong spin-orbit coupling, the microscopic origin of the spin-orbit potential remains elusive, owing to its dependence on the resolution scale and renormalization scheme of nuclear forces. Here, we investigate the evolution of shell structure with varying momentum resolution in nuclear interactions derived from chiral effective field theory, using the similarity renormalization group to link different scales. We uncover a novel transition from spin symmetry to pseudospin symmetry as the resolution scale decreases, during which magic numbers emerge naturally. A similar pattern is found in calculations using relativistic one-boson-exchange potentials, underscoring the robustness of the phenomenon. This establishes a direct connection between realistic nuclear forces with a high resolution scale and effective nuclear forces at coarse-grained scales, offering a first-principles explanation for the origin of magic numbers and pseudospin symmetry in nuclear shell structure, and new insights into the structure of exotic nuclei far from stability. - oai:arXiv.org:2504.09148v2 - nucl-th - nucl-ex + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/8lzc-j1lx - C. R. Ding, C. C. Wang, J. M. Yao, H. Hergert, H. Z. Liang, S. Bogner + C\'edric Pilatte - Thermal modifications of mesons and energy-energy correlators from real-time simulations of a $U(1)$ lattice gauge theory - https://arxiv.org/abs/2507.16890 - arXiv:2507.16890v2 Announce Type: replace-cross -Abstract: We investigate thermal properties of a $U(1)$ lattice gauge theory in $1+1$-dimensions through real-time simulations. We extract the spectral functions directly coupling to the pseudoscalar and scalar mesons, demonstrating the thermal modifications of these states with increasing temperatures. Introducing the notion of energy-flow operators, we quantify the temporal build-up of correlations in the energy flows across the lattice. We demonstrate that energy-energy correlators fail to factorize to products of energy flows, both in the vacuum and at nonzero-temperature, indicating the presence of non-trivial correlations in the quantum states. Our results constitute a first real-time \textit{ab-initio} study of bound state thermal broadening and finite temperature energy-flow correlations in a gauge theory, providing a benchmark for future studies of hadronic matter under extreme conditions. - oai:arXiv.org:2507.16890v2 - hep-ph - hep-lat + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/x3sn-vq11 - Phys. Rev. D 112, 114505 (2025) - Jo\~ao Barata, David Frenklakh, Swagato Mukherjee + Tierui Gong, Chau Yuen, Chong Meng Samson See, M\'erouane Debbah, Lajos Hanzo - Quantum interferometry in external gravitational fields - https://arxiv.org/abs/2507.21808 - arXiv:2507.21808v3 Announce Type: replace-cross -Abstract: Current models of quantum interference experiments in external gravitational fields lack a common framework: while matter-wave interferometers are commonly described using the Schr\"odinger equation with a Newtonian potential, gravitational effects in quantum optics are modeled using either post-Newtonian metrics or highly symmetric exact solutions to Einstein's field equations such as those of Schwarzschild and Kerr. To coherently describe both kinds of experiments, this paper develops a unified framework for modeling quantum interferometers in general stationary space-times. This model provides a rigorous description and coherent interpretation of the effects of classical gravity on quantum probes. - oai:arXiv.org:2507.21808v3 - gr-qc + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - 10.1103/8dsx-jt6b - Phys. Rev. A 112, 062211 (2025) - Thomas B. Mieling, Thomas Morling, Christopher Hilweg, Philip Walther + 10.1364/AO.578189 + A. S. Dyatlov, M. A. Nozdrin, A. N. Sergeev, N. E. Sheremet, S. S. Stafeev, D. V. Karlovets - Nitrogen-Vacancy Emission from Nanodiamond: Size, Depth, and Surroundings - https://arxiv.org/abs/2508.08565 - arXiv:2508.08565v3 Announce Type: replace-cross -Abstract: The negatively charged nitrogen-vacancy (NV) center in diamond is a leading solid-state quantum emitter, offering spin-photon interfaces over a wide temperature range with applications from electromagnetic sensing to bioimaging. While NV centers in bulk diamond are well understood, embedding them in nanodiamond (ND) introduces complexities from size, NV location, and NV polarizations. NVs in ND show altered fluorescence properties including longer lifetimes, lower quantum efficiency, and higher sensitivity to dielectric surroundings, which arise from radiative suppression, surface-induced non-radiative decay, and escape inefficiency at the diamond-background interface. Prior models typically addressed isolated aspects, such as dielectric contrast or surface quenching, without integrating full quantum-optical NV behavior with classical electrodynamics. We present a hybrid framework coupling rigorous electromagnetic simulations with a quantum-optical NV model including phonon sideband dynamics. NV emission is found to depend strongly on ND size, NV position, and surrounding refractive index. Our results explain observations such as shallow NVs in water-coated ND appearing brighter than deeper ones in air. This integrated model provides a unified framework for realistic NV in ND emission scenarios and informs the design of efficient NV-based sensors and quantum devices, advancing understanding of quantum emitter photophysics in nanoscale crystals. - oai:arXiv.org:2508.08565v3 - physics.optics + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1002/andp.202500367 - Annalen der Physik,2025;0:e00367 - Harini Hapuarachchi, Francesco Campaioli, Jared H Cole, Andrew D Greentree, Qiang Sun + 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 - Vacuum Energy and Topological Mass from a Constant Magnetic Field and Boundary Conditions in Coupled Scalar Field Theories - https://arxiv.org/abs/2508.15121 - arXiv:2508.15121v3 Announce Type: replace-cross -Abstract: We investigate the combined effects of a uniform magnetic field and boundary conditions on vacuum energy and topological mass generation in a coupled scalar field theory. The system consists of a real scalar field, subject to Dirichlet boundary conditions, interacting via self- and cross-couplings with a gauge-coupled complex scalar field obeying mixed boundary conditions between two perfectly reflecting parallel plates. The magnetic field induces Landau quantization, leading to novel contributions. Employing zeta-function regularization within the effective potential formalism, we derive the renormalized effective potential up to second order in the coupling constants without imposing a vanishing magnetic field in the renormalization scheme. Our renormalization approach preserves magnetic contributions while properly removing divergences, enabling a consistent treatment of finite-size corrections, magnetic effects, and interaction terms. We compute the vacuum energy per unit area of the plates, analyze the emergence of a topological mass from boundary and magnetic contributions, and evaluate the first-order coupling-constant corrections at two-loop order. Detailed asymptotic analysis are presented for both weak- and strong-field regimes, revealing exponential suppression at high magnetic fields and nontrivial polynomial and logarithmic behavior in the weak-field limit. - oai:arXiv.org:2508.15121v3 + 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-ph - math.MP + math.RT quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by/4.0/ - A. J. D. Farias Junior, Andrea Erdas, Herondy F. Santana Mota + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Anatoly Dymarsky, Johan Henriksson, Brian McPeak - A Continuous Energy Ising Machine Leveraging Difference-of-Convex Programming - https://arxiv.org/abs/2509.01928 - arXiv:2509.01928v2 Announce Type: replace-cross -Abstract: Many combinatorial optimization problems can be reformulated as finding the ground state of the Ising model. Existing Ising solvers are mostly inspired by simulated annealing. Although annealing techniques offer scalability, they lack convergence guarantees and are sensitive to the cooling schedule. We propose solving the Ising problem by relaxing the binary spins to continuous variables and introducing an attraction potential that steers the solution toward binary spin configurations. A key property of this potential is that its combination with the Ising energy produces a Hamiltonian that can be written as a difference of convex polynomials. This enables us to design efficient iterative algorithms that require a single matrix-vector multiplication per iteration and provide convergence guarantees. We implement our Ising solver on a wide range of GPU platforms, from edge devices to high-performance computing clusters, and demonstrate that it consistently outperforms existing solvers across problem sizes ranging from small ($10^3$ spins) to ultra-large ($10^8$ spins). - oai:arXiv.org:2509.01928v2 - cs.DC - math-ph - math.MP - math.OC + 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 + cond-mat.mes-hall + cond-mat.str-el quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Debraj Banerjee, Santanu Mahapatra, Kunal Narayan Chaudhury + Fabian J. Pauw, Ulrich Schollw\"ock, Nathan Goldman, Sebastian Paeckel, Felix A. Palm - Photonic Exceptional Points in Holography and QCD - https://arxiv.org/abs/2510.15518 - arXiv:2510.15518v4 Announce Type: replace-cross -Abstract: In this work, based on an analogy of holographic confining geometries and using complexified fields, we build the holographic toy model of third order photonic exceptional points (EPs) of ternary coupled microrings with gain and loss, which makes an open, non-Hermitian quantum system. In our model, we discuss the Ferrell-Glover-Tinkham sum rule for various combinations of gain and loss systems, and numerically find the behavior of spectra which matches with the experiments. We also discuss the inhomogeneous case of a holographic lattice for three-site photonic EPs. Additionally, in our holographic model, we numerically find the behavior of phase rigidity and the Petermann factor around EPs versus various parameters of the model. We also discuss the connections between recent developments in complexified, time-dependent entanglement entropy and EPs, and finally, we connect EPs and the $\theta$-vacuum of QCD through topological structures, partition functions, and winding numbers, and find a second-order EP in a perturbed $\theta$-vacuum model. - oai:arXiv.org:2510.15518v4 - hep-th + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Mahdis Ghodrati + Daniele Ferretti, Kalle Koskinen - Group Representations of Lorentz Transformations Extended to Superluminal Observers - https://arxiv.org/abs/2510.25385 - arXiv:2510.25385v3 Announce Type: replace-cross -Abstract: We construct an extension of the proper orthochronous Lorentz group that includes space-time transformations for observers moving with superluminal relative velocities in arbitrary direction. This extension is generated by a realization of the Klein four group depending on polar and azimuthal angles identifying a spatial direction and is obtained with matrices representing infinite velocity limits of superluminal Lorentz boosts. The resulting group has the same identity component of the whole Lorentz group O(3,1) but involutive operators corresponding to an infinite speed boost and its negative in place of parity and time reversal. Different spatial directions in the definition of Klein group realization give rise to equivalent group extensions. We then define the extended Poincare group including translations and classify its unitary irreducible representations (UIRs). The resulting UIRs are induced from Wigner's UIRs of standard Poincare group and depend on the action of the extended Lorentz group defined on momentum space. UIRs corresponding to non lightlike orbits restrict to the ordinary Poincare subgroup as a multiplicity one direct sum of a massive forward, a massive backward and a tachyonic Wigner UIR while for lightlike orbits as two inequivalent direct sum representations combiningh linearly a forward and backward massless Wigner UIR. We then derive wave equations corresponding to solutions of the Casimir eigenvalue problem of Poincare algebra obtained differentiating the above representations. This set of equations contains all the wave equations known to date in quantum field theory together with new wave equations describing tachyonic behaviour and a new class of massless representations. We finally show that tachyonic wave functions provide a relevant representation theoretic tool for interpretation of parity violation phenomena in quantum field theory - oai:arXiv.org:2510.25385v3 - hep-th + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/publicdomain/zero/1.0/ - Marco Zaopo + 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 - Quantum-coherent optical isolation and circulation using frequency conversion on a chip - https://arxiv.org/abs/2511.00570 - arXiv:2511.00570v2 Announce Type: replace-cross -Abstract: Breaking optical reciprocity enables new regimes of light--matter interaction with broad implications for fundamental physics and emerging quantum technologies. Although various approaches have been explored to achieve optical nonreciprocity, realizing it at the single-photon level has remained a major challenge. Here, we demonstrate nonmagnetic optical nonreciprocity -- including both isolation and circulation -- in the quantum regime, enabled by efficient and noiseless all-optical frequency conversion on an integrated III-V photonic chip. Our device preserves the quantum coherence and entanglement of the input photons while delivering exceptional performance parameters, including a high extinction ratio of 34 dB, low insertion loss of 0.8 dB, broad bandwidth of 44 GHz, high operational fidelity of 97%, and widely tunable operation wavelength. This realization of quantum optical nonreciprocity in a scalable photonic platform opens a pathway toward directional quantum communication and noise-resilient quantum networks. - oai:arXiv.org:2511.00570v2 - physics.optics + 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 + math-ph + math.MP + math.OA quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jierui Hu, Hao Yuan, Joshua Akin, Shanhui Fan, Kejie Fang + Gergely Bunth, J\'ozsef Pitrik, Tam\'as Titkos, D\'aniel Virosztek - Inductive van der Waals Force between Two Quantum Loops - https://arxiv.org/abs/2512.01263 - arXiv:2512.01263v2 Announce Type: replace-cross -Abstract: We study the van der Waals-London force, which is typically associated with fluctuating dipoles in atoms, in a mesoscopic circuit consisting of two inductively coupled superconducting loops. We investigate the ``inductive" van der Waals-London interaction using both semiclassical and quantum electrodynamic (QED) approaches. The semiclassical model predicts a repulsive interaction due to anticorrelated current fluctuations. In contrast, the QED framework, which incorporates virtual photon exchange, reveals a predominantly attractive force. A key contribution comes from a state-independent two-photon exchange, which is absent in the semiclassical description and undetectable by spectroscopy. Our study introduces a new experimental platform for measuring the van der Waals force between individual artificial atoms via controlled mesoscopic circuits. - oai:arXiv.org:2512.01263v2 - cond-mat.mes-hall + 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 quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 - replace-cross - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Kicheon Kang - - - Real-Time Dynamics in Two Dimensions with Tensor Network States via Time-Dependent Variational Monte Carlo - https://arxiv.org/abs/2512.06768 - arXiv:2512.06768v2 Announce Type: replace-cross -Abstract: Reliably simulating two-dimensional many-body quantum dynamics with projected entangled pair states (PEPS) has long been a difficult challenge. In this work, we overcome this barrier for low-energy quantum dynamics by developing a stable and efficient time-dependent variational Monte Carlo (tVMC) framework for PEPS. By analytically removing all gauge redundancies of the PEPS manifold and exploiting tensor locality, we obtain a numerically well-conditioned stochastic reconfiguration (SR) equation amenable to robust solution using the efficient Cholesky decomposition, enabling long-time evolution in previously inaccessible regimes. We demonstrate the power and generality of the method through four representative real-time problems in two dimensions: (I) chiral edge propagation in a free-fermion Chern insulator; (II) fractionalized charge transport in a fractional Chern insulator; (III) vison confinement dynamics in the Higgs phase of a Z2 lattice gauge theory; and (IV) superfluidity and critical velocity in interacting bosons. All simulations are performed on 12x12 or 13x13 lattices with evolution times T = 10 to 12 using modest computational resources (1 to 5 days on a single GPU card). Where exact benchmarks exist (case I), PEPS-tVMC matches free-fermion dynamics with high accuracy up to T = 12. These results establish PEPS-tVMC as a practical and versatile tool for real-time quantum dynamics in two dimensions. The method extends the reach of classical tensor-network simulations for studying elementary excitations in quantum many-body systems and provides a valuable computational counterpart to emerging quantum simulators. - oai:arXiv.org:2512.06768v2 - cond-mat.str-el - cond-mat.stat-mech - quant-ph - Thu, 11 Dec 2025 00:00:00 -0500 + Fri, 12 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Yantao Wu + http://creativecommons.org/licenses/by/4.0/ + Naman Jain, Jin Zhang, Marcus Culemann, Philipp M. Preiss