Quantum Physics
Brazilian Twin Photons 32nd anniversary
Renné Medeiros de Araújo, Raphael César Souza Pimenta, Lucas Marques Fagundes et al. (+4 more)
We present a historical review of the development and impact of spontaneous parametric down-conversion (SPDC) in Brazil, marking over three decades since the first twin-
photon experiments were performed in the country. This article traces the pioneering efforts that initiated the field, highlighting key experiments, institutions, and researchers who contributed to its growth. We discuss seminal works that established SPDC as a fundamental tool in the Brazilian
Quantum Optics community, including studies on spatial correlations,
entanglement, and decoherence. By presenting a curated sequence of experiments, we offer an overview of how Brazilian research in twin-
photon systems has explored profound concepts through fundamental demonstrations, leading to significant international impact. This review also highlights the formation of a strong scientific community and its ongoing efforts to turn fundamental knowledge into
quantum applications.
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All authors Renné Medeiros de Araújo, Raphael César Souza Pimenta, Lucas Marques Fagundes, Gustavo Henrique dos Santos, Nara Rubiano da Silva, Stephen Patrick Walborn, Paulo Henrique Souto Ribeiro
Quantum Physics
Single-Operation Rydberg Phase Gates via Dynamic Population Suppression
Sebastian C. Carrasco, Jabir Chathanathil, Svetlana A. Malinovskaya et al. (+2 more)
We propose a versatile control protocol based on modulated zero-pulse-area fields that dynamically suppresses Rydberg excitation while retaining Rydberg-Rydberg interactions as an entangling phase resource. This mechanism enables single-step, perfectly entangling phase gates for arbitrary blockade strengths, eliminating finite-blockade errors even when the Rabi frequency approaches or exceeds the interaction energy. The approach defines a new operational regime for Rydberg-blockade
quantum logic in which speed, fidelity, and robustness are achieved simultaneously within a simple dynamical framework. Owing to its simplicity and generality, the technique is compatible with a wide range of neutral-atom architectures and offers a promising route toward scalable, high-fidelity
quantum computation and simulation.
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All authors Sebastian C. Carrasco, Jabir Chathanathil, Svetlana A. Malinovskaya, Ignacio Sola, Vladimir S. Malinovsky
Quantum Physics · Cross-listed from cond-mat.supr-con
Robustness of flat band superconductivity against disorder in a two-dimensional Lieb lattice model
Georges Bouzerar and Maxime Thumin
Recently, the possibility of high-temperature superconductivity (SC) in flat-band (FB) systems has been the focus of a great deal of activity. This study reveals that unlike conventional intra-band SC for which disorder has a dramatic impact, that associated with FBs is surprisingly robust to disorder-induced fluctuations and quasi-particle localization. In particular, for weak off-diagonal disorder, the critical temperature decreases linearly with disorder amplitude for conventional SC, whereas it is only quadratic in the case of SC in FBs. Our findings could have a major impact on the research and development of new compounds whose high purity will no longer be a critical barrier to their synthesis.
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Quantum Physics · Cross-listed from cond-mat.mes-hall
Mesoscopic superfluid to superconductor transition
Yehoshua Winsten and Doron Cohen
Spectrum
tomography for the energy ($E$) of a ring-shaped Bose-Hubbard
circuit is illustrated. There is an inter-particle interaction $U$ that controls superfluidity (SF) and the transition to the Mott
Insulator (MI) regime. The
circuit is coupled to an electromagnetic cavity mode of frequency $\omega_0$, and the coupling is characterized by a generalized fine-structure-constant $\alpha$ that controls the emergence of superconductivity (SC). The ${(U,\alpha,\omega_0,E)}$ diagram features SF and SC regions, a vast region of fragmented possibly chaotic states, and an MI regime for large $U$. The mesoscopic version of the Meissner effect and the Anderson-
Higgs mechanism are discussed.
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Quantum Physics
Enhanced charging power in nonreciprocal quantum battery by reservoir engineering
Qi-Yin Lin, Guang-Zheng Ye, Can Li et al. (+2 more)
We propose a scheme to achieve a nonreciprocal
quantum battery (QB) in the non-Hermitian (NH) system, which can overcome the intrinsic dissipation and reverse flow constraints. The design is based on a charger and a battery, which are coherently coupled and jointly interact with a bad cavity. By introducing the auxiliary bad cavity and exploiting the nonreciprocal condition, this model can harness the environmental dissipation to suppress the reverse energy transfer. Under resonant conditions, we have achieved a four ratio of the battery energy to the charger energy; in contrast, this ratio is significantly reduced under large detuning. Through damping optimization, high efficiency of the short-time charging power is attained. In comparison to the fully nonreciprocal scheme, the QB operating at the exceptional point (EP) exhibits greater resilience to parameter fluctuations. These findings highlight the potential of NH
quantum engineering for advancing QB technology, particularly in regimes involving directional energy transfer, controlled dissipation, and
entropy management in open
quantum systems.
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All authors Qi-Yin Lin, Guang-Zheng Ye, Can Li, Wan-Jun Su, Huai-Zhi Wu
Quantum Physics
Quantum Diamond Microscopy for Non-Destructive Failure Analysis of an Integrated Fan-Out Package-on-Package iPhone Chip
Bartu Bisgin, Marwa Garsi, Andreas Welscher et al. (+2 more)
The increasing complexity of advanced
semiconductor packages, driven by chiplet architectures and 2.5D/3D integration, challenges conventional failure localization methods such as lock-in thermography (LIT) and complicates current Failure Analysis (FA) workflows. Dense redistribution layers and buried interconnects limit the ability of established techniques to understand failure mechanisms non-destructively. In this work, we validate
quantum diamond microscopy (QDM) based on nitrogen-vacancy (NV) centers in diamond as a non-destructive localization method through
magnetic current path imaging at the package level. Using commercial Integrated Fan-Out Package-on- Package (InFO-PoP) devices from iPhones, we showcase a complete FA workflow that includes QDM to localize a short-type failure at an Integrated Passive Device (IPD) at the package backside. We showcase that the QDM results provide invaluable information on top of conventional techniques and can significantly enhance root-cause identification in package-level FA workflows. This work demonstrates the potential of QDM for broader integration into
semiconductor chip and package analysis workflows.
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All authors Bartu Bisgin, Marwa Garsi, Andreas Welscher, Michael Hanke, Fleming Bruckmaier
Quantum Physics
Sharp values for all dynamical variables via Anti-Wick quantization
Simon Friederich
This paper proposes an approach to interpreting
quantum expectation values that may help address the
quantum measurement problem.
Quantum expectation values are usually calculated via
Hilbert space inner products and, thereby, differently from expectation values in classical mechanics, which are weighted phase-space integrals. It is shown that, by using Anti-Wick quantization to associate dynamical variables with self-adjoint linear operators,
quantum expectation values can be interpreted as genuine weighted averages over phase space, paralleling their classical counterparts. This interpretation arises naturally in the Segal-Bargmann space, where creation and annihilation operators act as simple multiplication and differentiation operators. In this setting, the Husimi Q-function - the coherent-state representation of the
quantum state - can be seen as a true probability density in phase space. Unlike Bohmian mechanics, the present approach retains the standard correspondence between dynamical variables and self-adjoint operators while paving the way for a classical-like probabilistic interpretation of
quantum statistics.
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Quantum Physics · Cross-listed from physics.flu-dyn
Tensor Network Lattice Boltzmann Method for Data-Compressed Fluid Simulations
Lukas Gross, Elie Mounzer, David M. Wawrzyniak et al. (+2 more)
Resolving unsteady transport phenomena in geometrically complex domains is traditionally constrained by
polynomial scaling of computational cost with spatial resolution. While methods based on tensor-network data representations or
matrix-product states (MPS) data encodings have emerged as a technique to systematically reduce degrees of freedom, existing formulations do not extend to complex geometries and complex flow physics. Both capabilities are offered by
lattice Boltzmann methods, for which we develop a generalized MPS formulation. This development marks a paradigm shift from classical methods that rely on explicit grid refinement for data reduction. Instead, our approach exploits non-local correlations in the MPS representation to systemically compress the global fluid state directly without modifying the underlying grid. We
benchmark the proposed solver against classical LBM using three-dimensional flows through structured media and vascular geometries. The results confirm that the MPS formulation reproduces the reference solution with high fidelity while achieving compression ratios exceeding two orders of magnitude, positioning tensor networks or MPS encodings as a scalable paradigm for continuum mechanics on high-performance GPU hardware.
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All authors Lukas Gross, Elie Mounzer, David M. Wawrzyniak, Josef M. Winter, Nikolaus A. Adams
Quantum Physics
On-Demand Microwave Single-Photon Source Based on Tantalum Thin Film
Ying Hu, Sheng-Yong Li, En-Qi Chen et al. (+4 more)
Single-
photon sources are crucial for
quantum information technologies. Here, we demonstrate a microwave single-
photon source fabricated using a tantalum-based thin film, whose favorable material properties enable high-quality and stable
photon emission. The antibunching behavior of the emitted radiation is revealed by second-order correlation measurements. Furthermore, traveling-wave parametric amplifiers are used as the pre-amplifier in the detection chains, we substantially improve the signal-to-noise ratio and thereby greatly reduce the acquisition time required for second-order correlation measurements. These results demonstrate the viability of tantalum-based superconducting devices as reliable platforms for microwave
quantum photonics.
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All authors Ying Hu, Sheng-Yong Li, En-Qi Chen, Jing Zhang, Yu-xi Liu, Jia-Gui Feng, Zhihui Peng
Quantum Physics
Relativistic motion through a thermal bath as a thermodynamic resource
Rahul Shastri
We show that a localized
quantum system following an arbitrary stationary trajectory and weakly interacting with a stationary thermal bath of a massless scalar field is generically driven into a non-Gibbs steady state by relative motion alone, even without external driving or multiple baths. Relative motion between the system and the bath modifies the standard Kubo-Martin-Schwinger (KMS) relation, preventing relaxation to a Gibbs state. The resulting steady states fall into two distinct classes: (i) nonequilibrium steady states (NESS) with persistent probability currents, and (ii) current-free non-Gibbs steady states characterized by a frequency-dependent effective inverse temperature. We then focus on the simplest stationary trajectory, namely uniform relativistic motion with respect to a thermal bath. Using a three-level system as an illustrative example, we demonstrate that the former class can function as noisy
stochastic clocks, while the latter possesses finite nonequilibrium free energy, enabling work extraction or storage, highlighting their potential as
quantum batteries.
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Quantum Physics
Exponentially accelerated relaxation and quantum Mpemba effect in open quantum systems
Emerson Lima Caldas and Diego Paiva Pires
We investigate the
quantum Mpemba effect in the relaxation of open
quantum systems whose effective dynamics is described by Davies maps. We introduce a class of
unitary transformations constructed from permutation
matrices that, when applied to an initial state, (i) suppress the slowest decaying modes of the nonunitary dynamics and (ii) maximize the state's distinguishability from the steady state. The first condition ensures exponentially faster convergence to
equilibrium, while the second implies that a
quantum system initially further from
equilibrium can approach it more rapidly than one that starts closer. This protocol thus realizes a genuine Mpemba effect, and its simulation requires low computational effort. We prove that, for any initial state, there exists a permutation
matrix that maximizes its distance from
equilibrium with respect to a chosen information-theoretic distinguishability measure. We illustrate our findings for a two-level system, as well as for the nonunitary dynamics of the transverse-field Ising chain and the XXZ chain, each weakly coupled to a bosonic thermal bath. In these cases, the
quantum Mpemba effect is demonstrated using the
Hilbert-Schmidt distance,
quantum relative
entropy, and trace distance. Overall, our results provide a versatile framework for engineering a genuine
quantum Mpemba effect in Markovian open
quantum systems.
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Quantum Physics · Cross-listed from physics.optics
Site-controlled quantum dot arrays edge-coupled to integrated silicon nitride waveguides and devices
John O'Hara, Nicola Maraviglia, Mack Johnson et al. (+7 more)
The scalability of
quantum photonic integrated
circuits opens the path towards large-scale
quantum computing and communication. To date, this scalability has been limited by the
stochastic nature of the
quantum light sources. Moreover, hybrid integration of different platforms will likely be necessary to combine state-of-the-art devices into a functioning architecture. Here, we demonstrate the active
alignment and edge-coupling of arrays of ten site-controlled gallium arsenide
quantum dots to an array of ten silicon nitride single-mode waveguides, at cryogenic temperatures. The coupling is facilitated by the fabrication of nanopillars, deterministically self-aligned around each
quantum dot, leading to a high-yield and regular array of single-
photon sources. An on-chip beamsplitter verifies the triggered emission of single
photons into the silicon nitride chip. The low inhomogeneous broadening of the ensemble enables us to observe the spectral overlap of adjacent site-controlled emitters. Across the array of waveguides, the signal collected from each coupled
quantum dot is consistently and reproducibly 0.17 relative to the free-space collection from the very same single-
photon source. Comparing measurement with waveguide simulations, we infer that absolute coupling efficiencies of $\approx 5 \%$ are currently obtained between our
quantum dots and the waveguides.
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All authors John O'Hara, Nicola Maraviglia, Mack Johnson, Jesper Håkansson, Salvador Medina, Gediminas Juska, Luca Colavecchi, Frank H. Peters, Brian Corbett, Emanuele Pelucchi
Quantum Physics
Mediated Transmission of Quantum Synchronization in Star Networks
Shuo Dai and Ran Qi
Synchronization transmission describes the emergence of coherence between two uncoupled oscillators mediated by their mutual coupling to an intermediate one. In classical
star networks, such mediated coupling gives rise to remote synchronization–where nonadjacent leaf nodes synchronize through a nonsynchronous hub–and to explosive synchronization, characterized by an abrupt collective transition to coherence. In the
quantum regime, analogous effects can arise from the interplay between 1:1 phase locking and 2:1 phase-locking blockade in coupled
spin-1 particles. In this work, we investigate a
star network composed of
spin-1 particles. For identical oscillators, symmetric and asymmetric dissipation lead to distinct transmission behaviors: remote synchronization and quasi-explosive synchronization appear in different coupling regimes, a phenomenon absent in classical counterparts. For nonidentical networks, we find that at large detuning remote synchronization emerges in the weak-coupling regime and evolves into quasi-explosive synchronization as the coupling increases, consistent with classical
star-network dynamics. These findings reveal the rich dynamical characteristics of mediated
quantum synchronization and point toward new possibilities for exploring synchronization transmission in larger and more complex
quantum systems.
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Quantum Physics · Cross-listed from physics.optics
Anomalous Wave-Packet Dynamics in One-Dimensional Non-Hermitian Lattices
Yanyan He and Tomoki Ozawa
Non-Hermitian (NH) systems have attracted great
attention due to their exotic phenomena beyond Hermitian domains. Here we study the wave-packet dynamics in general one-dimensional NH
lattices and uncover several unexpected phenomena. The group velocity of a wave packet during the time
evolution in such NH
lattices is not only governed by the real part of the band structure but also by its imaginary part. The momentum also evolves due to the imaginary part of the band structure, which can lead to a self-induced Bloch oscillation in the absence of external fields. Furthermore, we discover the wave-packet dynamics can exhibit disorder-free NH jumps even when the energy spectra are entirely real. Finally, we show that the NH jumps can lead to both positive and negative temporal Goos–Hänchen shifts at the edge.
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Quantum Physics
RuleSet Generation Framework for Application Layer Integration in Quantum Internet
Rei Kawano, Shin Nishio, Hideaki Kawaguchi et al. (+2 more)
Layered architectures for the
Quantum Internet have been proposed, inspired by that of the classical Internet, which has demonstrated high maintainability even in large-scale systems. While lower layers in the
Quantum Internet, such as
entanglement generation and distribution, have been extensively studied, the application layer - responsible for translating user requests into executable
quantum-network operations - remains largely unexplored. A significant challenge is translating application-level requests into the concrete instructions executable at lower layers. In this work, we introduce a RuleSet-based framework that explicitly incorporates the application layer into the layered architecture of the
Quantum Internet. Our framework builds on a RuleSet-based protocol, clarifying communication procedures, organizing application request information, and introducing new Rules for application execution by
embedding application specifications into RuleSets. To evaluate feasibility, we constructed state machines from the generated RuleSets. This approach enables a transparent integration from the application layer down to the physical layer, thereby lowering barriers to deploying new applications on the
Quantum Internet.
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All authors Rei Kawano, Shin Nishio, Hideaki Kawaguchi, Shota Nagayama, Takahiko Satoh
Quantum Physics
On the emergence of preferred structures in quantum theory
Antoine Soulas, Guilherme Franzmann and Andrea Di Biagio
We assess the possibilities offered by
Hilbert space fundamentalism, an attitude towards
quantum physics according to which all physical structures (e.g. subsystems, locality, spacetime, preferred observables) should emerge from minimal
quantum ingredients (typically a
Hilbert space,
Hamiltonian, and state). As a case study, we first mainly focus on the specific question of whether the
Hamiltonian can uniquely determine a tensor product structure, a crucial challenge in the growing field of
quantum mereology. The present paper reviews, clarifies, and critically examines two apparently conflicting
theorems by Cotler et al. and Stoica. We resolve the tension, show how the former has been widely misinterpreted and why the latter is correct only in some weaker version. We then propose a correct mathematical way to address the general problem of preferred structures in
quantum theory, relative to the characterization of emergent objects by
unitary-invariant properties. Finally, we apply this formalism in the particular case we started with, and show that a
Hamiltonian and a state are enough structure to uniquely select a preferred tensor product structure.
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Quantum Physics
Resonator-assisted single-photon frequency convertion in a conventional waveguide with a giant V-type atom
Ge Sun, Hongzheng Wu, Jing Lu et al. (+1 more)
We propose a scheme to achieve efficient frequency conversion for a single
photon propagating in a 1D conventional waveguide by exploiting the
quantum interference induced by the scale of a V-type
giant atom (GA) characterized by the distance between the two coupling points as well as single-
photon transition pathways originated from the coupling between the GA and the resonator. The presence of
photons in the resonator triggers the frequency conversion of
photons. The scattering spectra and the conversion contrast are studied in both the Markovian and the non-Markovian regimes. The disappearance of frequency conversion is rooted in the complete suppression of the emission from the excited state to either of lower states in the $n+1$ subspace where $n$ is the
photon number of the resonator, and the non-Markovicity-induced nonreciprocity is found under specific conditions. Altering the
photon number $n$ induces the non-reciprocal transmission of single
photons in the waveguide, hence, enhance the conversion probability.
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All authors Ge Sun, Hongzheng Wu, Jing Lu, Lan Zhou
Quantum Physics · Cross-listed from cond-mat.mtrl-sci
Multiplet structure of chromium(III) dopants in wide band gap materials
Ilya Popov, Petros-Panagis Filippatos, Shayantan Chaudhuri et al. (+3 more)
Transition metal doping is commonly used for altering the properties of solid-state materials to suit applications in science and technology. Partially filled $d$-shells of transition metal atoms lead to electronic states with diverse spatial and
spin symmetries. Chromium(III) cations have shown great potential for designing
laser materials and, more recently, for developing
spin qubits in
quantum applications. They also represent an intriguing class of chemical systems with strongly correlated multi-reference excited states, due to the $d^3$ electron configuration. These states are difficult to describe accurately using single-reference
quantum chemical methods such as density functional theory (DFT), the most commonly used method to study the electronic structures of solid-state systems. Recently, the periodic effective
Hamiltonian of
crystal field (pEHCF) method has been shown to overcome some limitations arising in the calculations of excited $d$-states. In this work, we assess the suitability of DFT and pEHCF to calculate the electronic structure and $d$-$d$ excitations of chromium(III) dopants in wide band gap host materials. The results will aid computational development of novel transition metal-doped materials and provide a deeper understanding of the complex nature of transition metal dopants in solids.
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All authors Ilya Popov, Petros-Panagis Filippatos, Shayantan Chaudhuri, Andrei L. Tchougréeff, Katherine Inzani, Elena Besley
Quantum Physics
Intrinsic non-Markovian magnetisation dynamics
Felix Hartmann, Vivek Unikandanunni, Matias Bargheer et al. (+3 more)
Memory effects are widespread in complex systems while evidence of non-Markovian dynamics in fundamental physical systems has been limited to specifically engineered cases. Here we report on the experimental observation of non-Markovian magnetisation dynamics in crystalline cobalt. Intense terahertz electromagnetic driving brings the system into a non-
equilibrium state, and allows us to follow its magnetisation dynamics in real time at low temperatures. The response reveals a striking multi-peaked frequency spectrum that defies conventional descriptions. Using open
quantum system theory we evidence that a non-Markovian
memory kernel, arising from
spin-
phonon bath coupling, naturally explains both the spectral structure and its temperature dependence. Theoretical prediction of the spectrum is accomplished by simulating the non-Markovian Landau-Lifshitz-Gilbert equation, while analytics quantitatively determines the frequencies of three spectral peaks. The results demonstrate that intrinsic
memory effects can emerge in a simple ferromagnet, opening new opportunities to explore and control non-Markovian dynamics in condensed-matter systems.
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All authors Felix Hartmann, Vivek Unikandanunni, Matias Bargheer, Eric E. Fullerton, Stefano Bonetti, Janet Anders
Quantum Physics
Dispersive readout with two orthogonal modes of a dielectric cavity
A.M. Kozodaev, I.S. Cojocaru, S.M. Drofa et al. (+8 more)
Nitrogen-vacancy color centers in diamond have proven themselves as a good, sensitive element for the measurement of
magnetic fields. While the mainstream of magnetometers based on NV centers uses so-called optically detected
magnetic resonance, there has recently been a suggestion to use dispersive readout of a dielectric cavity to enhance the sensitivity of magnetometers. Here, we demonstrate that the dispersive readout approach can be significantly improved if a two-channel scheme is considered.
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All authors A.M. Kozodaev, I.S. Cojocaru, S.M. Drofa, P.G. Vilyuzhanina, A. Chernyavskiy, V.G. Vins, A.N. Smolyaninov, S.Ya. Kilin, S.V. Bolshedvorskii, V.V. Soshenko, A.V. Akimov
Quantum Physics
Tunable Dynamics of a Dipolar Quantum Battery: Role of Spin-Spin Interactions and Coherence
J. Ramya Parkavi, R. Muthuganesan and V.K. Chandrasekar
This study explores the energy storage dynamics of a
quantum battery (QB) modeled using a dipolar
spin system with Dzyaloshinskii-Moriya (DM) interaction. We examine the performance of this system in terms of ergotropy, instantaneous power, capacity, and
quantum coherence using a two-
qubit model. By solving the system's time
evolution under cyclic
unitary processes, we analyze how external parameters such as temperature,
magnetic field, and DM interaction influence the charging behavior and
quantum resources of the battery. The findings demonstrate that
quantum coherence and DM interaction significantly enhance the energy storage efficiency and power output of the
quantum battery, offering promising strategies for designing high-performance
quantum energy storage devices. Furthermore, we investigate the performance of
quantum battery under the influence of a common dephasing environment, which limits the long-term work-extraction capability of dipolar
quantum batteries.
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Quantum Physics
33 Gbit/s source-device-independent quantum random number generator based on heterodyne detection with real-time FPGA-integrated extraction
Marius Cizauskas, Hamid Tebyanian, Mark Fox et al. (+3 more)
We present a high-speed continuous-variable
quantum random number generator (QRNG) based on heterodyne detection of
vacuum fluctuations. The scheme follows a source-device-independent (SDI) security model in which the
entropy originates from
quantum measurement uncertainty and no model of the source is required; security depends only on the trusted measurement device and the calibrated discretization, and thus remains valid even under
adversarial state preparation. The optical field is split by a 90$^\circ$ optical hybrid and measured by two balanced photodiodes to obtain both quadratures of the
vacuum state simultaneously. The analog outputs are digitized using a dual-channel 12-bit analog-to-digital converter operating at a sampling rate of 3.2 GS/s per channel, and processed in real time by an FPGA implementing Toeplitz hashing for randomness extraction. The
quantum-to-classical noise ratio was verified through calibrated power spectral density measurements and cross-checked in the time domain, confirming
vacuum-noise dominance within the 1.6 GHz detection bandwidth. After extraction, the system achieves a sustained generation rate of $R_{\rm net}= 33.92~\mathrm{Gbit/s}$ of uniformly distributed random bits, which pass all NIST and Dieharder statistical tests. The demonstrated platform provides a compact, FPGA-based realization of a practical heterodyne continuous-variable source-independent QRNG suitable for high-rate
quantum communication and secure key distribution systems.
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All authors Marius Cizauskas, Hamid Tebyanian, Mark Fox, Manfred Bayer, Marc Assmann, Alex Greilich
Quantum Physics
Revisiting Quantum Supremacy: Simulating Sycamore-Class Circuits Using Hybrid CPU/GPU HPC Workloads
Bob Wold and Venkateswaran Kasirajan
We present a framework for effectively simulating the execution of
quantum circuits originally designed to demonstrate
quantum supremacy using accessible high-performance computing (HPC) infrastructure. Building on prior CPU-only approaches, our pipeline combines a single NVIDIA A100 GPU for
quantum state construction, followed by N parallel CPU jobs that perform distributed measurement sampling. We validate the fidelity by simulating the 53-
qubit, 14-cycle Sycamore
circuit and achieving a linear cross-
entropy benchmarking (XEB) score of 0.549, exceeding the published XEB score of 0.002 from Google's reference data. We then evaluate execution time performance with the more complex 53-
qubit, 20-cycle
circuit, completing the full 2.5 million-shot workload over 100 CPU jobs in 01:15:36, representing a 6.95 x 10^7 speedup compared to Google's original classical estimate. Further, we show that if 1,000 CPU jobs were employed, the estimated duration would be approximately 00:17:35, only 12 minutes slower than the time taken by the original QPU-based experiment. These results illustrate that '
quantum supremacy' is not fixed and continues to be a moving target. In addition, hybrid classical-
quantum strategies may provide broader near-term
quantum utility than once thought.
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Quantum Physics
Zhiyuan Zhao, Qian Shi, Shaoyi Xu et al. (+8 more)
Identification of individual
cells within heterogeneous populations is essential for biomedical research and clinical diagnostics. Conventional labeling-based sorting methods, such as fluorescence-activated
cell sorting and
magnetic-activated
cell sorting, enable precise sorting when reliable markers are available. However, their applicability is limited in
cells lacking defined markers or sensitive to labeling, as labeling can compromise cellular viability and function. We present a single-
cell identification approach using
quantum-enhanced NMR with diamond nitrogen-vacancy centers for label-free detection of intracellular
proton ($^1$H) signals. Using this method, we distinguish two human tumor
cell lines by their
proton spin-
lattice ($T_1$) relaxation times, which serve as a
cell-intrinsic physicochemical signature. It lays the groundwork for label-free sorting applications in rare
cell analysis, personalized medicine, and single-
cell diagnostics.
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All authors Zhiyuan Zhao, Qian Shi, Shaoyi Xu, Xiangyu Ye, Mengze Shen, Jia Su, Ya Wang, Tianyu Xie, Qingsong Hu, Fazhan Shi, Jiangfeng Du
Quantum Physics
Simulating general noise nearly as cheaply as Pauli noise
Mark Myers II, Mariesa H. Teo, Rajesh Mishra et al. (+2 more)
Stabilizer simulation of Clifford
quantum circuits - error-correction
circuits, Clifford subroutines, etc. - on classical computers has played a central role in our understanding of
circuit performance. The stabilizer description, however, restricts the accessible noise one can incorporate into the simulation to Pauli-type noise. More general noise, including coherent errors, may have more severe impact on
circuit performance than Pauli noise; yet, such general noise have been difficult to access, much less investigate fully, in numerical simulations. Here, through the use of stratified importance sampling, we show how general noise can be simulated within the stabilizer formalism in reasonable time, with non-
unitary noise being nearly as cheap as Pauli noise.
Unitary (or coherent) noise can require an order of magnitude more time for the simulation, but nevertheless completes in very reasonable times, a drastic improvement over past approaches that typically fail to converge altogether. Our work thus enables detailed beyond-Pauli understanding of
circuit performance in the presence of real device noise, which is rarely Pauli in nature. Among other examples, we present direct simulation results for the performance of the popular rotated planar surface codes under
circuit-level general noise, previously available only in limited situations and/or through mappings to efficiently simulatable physical models.
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All authors Mark Myers II, Mariesa H. Teo, Rajesh Mishra, Jing Hao Chai, Hui Khoon Ng
Quantum Physics
Quantum geometrical effects in non-Hermitian systems
Anton Montag and Tomoki Ozawa
We explore the relation between
quantum geometry in non-Hermitian systems and physically measurable phenomena. We highlight various situations in which the behavior of a non-Hermitian system is best understood in terms of
quantum geometry, namely the notion of adiabatic potentials in non-Hermitian systems and the localization of Wannier states in periodic non-Hermitian systems. Further, we show that the non-Hermitian
quantum metric appears in the response of the system upon time-periodic modulation, which one can use to experimentally measure the non-Hermitian
quantum metric. We validate our results by providing numerical simulations of concrete exemplary systems.
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Quantum Physics
Non-Hermitian Bose-Hubbard-like quantum models
Miloslav Znojil
Among all of the non-Hermitian large-tridiagonal-
matrix quantum Hamiltonians we choose a subclass with the structure resembling the “
benchmark” realistic Bose-Hubbard model. We demonstrate that this choice can be declared user-friendly in the sense that the underlying singular values can be specified via a “Hermitized” Schrödinger-like equation. In particular, the related “Hermitized” Green's functions is shown given the two alternative compact and numerically efficient
matrix continued fraction forms.
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Quantum Physics · Cross-listed from cond-mat.stat-mech
Local Reversibility and Divergent Markov Length in 1+1-D Directed Percolation
Yu-Hsueh Chen and Tarun Grover
Recent progress in open many-body
quantum systems has highlighted the importance of the Markov length, the characteristic scale over which conditional correlations decay. It has been proposed that non-
equilibrium phases of matter can be defined as equivalence classes of states connected by short-time
evolution while maintaining a finite Markov length, a notion called local reversibility. A natural question is whether well-known classical models of non-
equilibrium criticality fit within this framework. Here we investigate the Domany-Kinzel model – which exhibits an active phase and an absorbing phase separated by a 1+1-D directed-percolation transition – from this information-theoretic perspective. Using tensor network simulations, we provide evidence for local reversibility within the active phase. Notably, the Markov length diverges upon approaching the critical point, unlike classical
equilibrium transitions where Markov length is zero due to their Gibbs character. Correspondingly, the conditional mutual information exhibits scaling consistent with directed percolation universality. Further, we analytically study the case of 1+1-D compact directed percolation, where the Markov length diverges throughout the phase diagram due to spontaneous breaking of domain-wall parity
symmetry from strong to weak. Nevertheless, the conditional mutual information continues to faithfully detect the corresponding phase transition.
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Quantum Physics
A versatile coherent Ising computing platform
Hai Wei, Chengjun Ai, Putuo Guo et al. (+12 more)
Coherent Ising Machines (CIMs) have emerged as a hybrid form of
quantum computing devices designed to solve NP-complete problems, offering an exciting opportunity for discovering optimal solutions. Despite challenges such as susceptibility to noise-induced local minima, we achieved notable advantages in improving the computational accuracy and stability of CIMs. We conducted a successful experimental demonstration of CIM via femto-second
laser pumping that integrates optimization strategies across optical and structural dimensions, resulting in significant performance enhancements. The results are particularly promising. An average success rate of 55% was achieved to identify optimal solutions within a Mobius Ladder graph comprising 100 vertices. Compared with other alternatives, the femto-second pulse results in significantly higher peak power, leading to more pronounced
quantum effects and lower pump power in optical fiber based CIMs. In addition, we have maintained an impressive success rate for a continuous period of 8 hours, emphasizing the practical applicability of CIMs in real-world scenarios. Furthermore, our research extends to the application of these principles in practical applications such as molecular docking and credit scoring. The results presented substantiate the theoretical promise of CIMs, paving the way for their integration into large-scale practical applications.
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All authors Hai Wei, Chengjun Ai, Putuo Guo, Bingjie Jia, Lixin Yuan, Hanquan Song, Shaobo Chen, Chongyu Cao, Jie Wu, Chao Ju, Yin Ma, Jintao Fan, Minglie Hu, Chuan Wang, Kai Wen
Quantum Physics
Beyond real: Investigating the role of complex numbers in self-testing
Ranyiliu Chen, Laura Mančinska and Jurij Volčič
We investigate complex self-testing, a generalization of standard self-testing that accounts for
quantum strategies whose statistics is indistinguishable from their complex conjugate's. We show that many structural results from standard self-testing extend to the complex setting, including lifting of common assumptions. Our main result is an operator-algebraic characterization: complex self-testing is equivalent to uniqueness of the real parts of higher moments, leading to a basis-independent formulation in terms of real C*
algebras. This leads to a classification of non-local strategies, and a tight boundary where standard self-testing does not apply and complex self-testing is necessary. We further construct a strategy involving quaternions, establishing the first standard self-test for genuinely complex strategy. Our work clarifies the structure of complex self-testing and highlights the subtle role of complex numbers in bipartite Bell non-locality.
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