Showing 1–50 of 194 results for author: Hu, J

An Efficient Explicit Implementation of a Quantum Algorithm with Quantum Advantage for Nonlinear Scalar Conservation Laws

Authors: Kezhen Wang, Junpeng Hu, Lei Zhang

Abstract: Quantum algorithms for nonlinear partial differential equations remain challenging because nonlinear dynamics are not directly amenable to unitary quantum simulation. Building on the level-set formulation, we construct a quantum algorithm and provide an explicit gate-level implementation for solving scalar conservation laws. The nonlinear equation is first lifted to a linear Liouville equation, di… ▽ More Quantum algorithms for nonlinear partial differential equations remain challenging because nonlinear dynamics are not directly amenable to unitary quantum simulation. Building on the level-set formulation, we construct a quantum algorithm and provide an explicit gate-level implementation for solving scalar conservation laws. The nonlinear equation is first lifted to a linear Liouville equation, discretized by finite differences, and then embedded into a unitary evolution through Schrödingerisation. We further develop quantum procedures for estimating relevant observables from the evolved state. Error bounds and gate-complexity estimates are established for the complete algorithm. The resulting complexity comparison demonstrates a quantum advantage for observable estimation in sufficiently high spatial dimensions, under standard assumptions on state preparation and oracle access. Finally, numerical experiments validate the accuracy, multidimensional applicability, and predicted scaling of the proposed method. △ Less

Submitted 10 August, 2026; originally announced August 2026.

Optimized Tensor-Network Renormalization for Quantum Dynamics: Resolving the Spectral Function of $\mathrm{K_2Co(SeO_3)_2}$

Authors: Jiahang Hu, Runze Chi, B. Normand, Hai-Jun Liao, T. Xiang

Abstract: Tensor-network methods have opened a powerful route for the study of dynamical spectral functions in two-dimensional quantum systems. However, existing approaches within the framework of infinite projected entangled-pair states construct the required renormalization tensors solely from the ground-state environment and can suffer from severe numerical instability. We identify the origin of this ins… ▽ More Tensor-network methods have opened a powerful route for the study of dynamical spectral functions in two-dimensional quantum systems. However, existing approaches within the framework of infinite projected entangled-pair states construct the required renormalization tensors solely from the ground-state environment and can suffer from severe numerical instability. We identify the origin of this instability and introduce an excitation-tailored corner-transfer-matrix renormalization-group (ET-CTMRG) method to resolve it. By incorporating excitation tensors into the renormalization procedure, the method constructs a substantially more accurate effective Hamiltonian matrix and thereby yields reliable and well-converged excitation spectra. For Heisenberg antiferromagnets, it reduces truncation errors by orders of magnitude and for the particularly complex case of the supersolid phase in the triangular-lattice XXZ magnet $\mathrm{K_2Co(SeO_3)_2}$, it achieves excellent quantitative agreement with inelastic neutron-scattering measurements. ET-CTMRG therefore provides a robust framework for investigating the dynamical properties of strongly correlated quantum systems. △ Less

Submitted 3 August, 2026; originally announced August 2026.

Comments: 17 pages, 13 figures

Controlling Atom Array in an Ultra-high-cooperativity Optical Cavity

Authors: Jilai Ye, Zhihao Chi, Ye Tian, Shuyao Mei, Xiaoyu Li, Wenjun Zhang, Yajuan Zhao, Jiazhong Hu, Wenlan Chen

Abstract: Neutral-atom array and cavity quantum electrodynamics offer complementary strengths for quantum science: scalable, reconfigurable qubit architectures and strong coherent light-matter coupling. Combining them in a single platform requires an optical cavity with simultaneously high cooperativity, sufficient mode volume to accommodate atom array, and ample side optical access for atom trapping, imagi… ▽ More Neutral-atom array and cavity quantum electrodynamics offer complementary strengths for quantum science: scalable, reconfigurable qubit architectures and strong coherent light-matter coupling. Combining them in a single platform requires an optical cavity with simultaneously high cooperativity, sufficient mode volume to accommodate atom array, and ample side optical access for atom trapping, imaging, cooling, and rearrangement, a combination that is challenging to achieve. Here we realize an atomic array integrated with a millimeter-scale Fabry--Pérot cavity whose optically-characterized single-atom cooperativity reaches $η_{\mathrm{cav}}=125\pm13$. Atom-cavity transmission spectra of trapped atoms yield an effective spectroscopic cooperativity $η_{\mathrm{spec}}=112.3\pm3.3$, providing an in-situ verification of strong coupling in the integrated platform, and we demonstrate simultaneous coupling of up to 16 individually trapped atoms to the antinode of the cavity mode. The key technical advance is a two-step mirror-fabrication method combining precision mechanical shaping and carbon-dioxide laser polishing, which produces concave fused-silica mirrors with sub-millimeter radii of curvature and residual roughness below 2 Å. Our results establish a regime of cavity-integrated atomic array that simultaneously provides high cooperativity, large mode volume, and flexible manipulation of individual atoms, opening opportunities for cavity-assisted quantum state readout and long-range entanglement-engineering in atom-array platforms. △ Less

Submitted 4 July, 2026; originally announced July 2026.

Comments: 6 pages,3 figures

Matter-wave Induced Transparency

Authors: Tongkang wang, Yuqi Liu, Wenlan Chen, Zhendong Zhang, Jiazhong Hu

Abstract: Electromagnetically induced transparency suppresses optical absorption through destructive interference, playing a central role in light-matter interaction and quantum information science. We report matter-wave induced transparency, where atomic collisional interactions induce transmission through a lossy molecular potential for the incident atomic scattering waves. Using cesium Bose-Einstein cond… ▽ More Electromagnetically induced transparency suppresses optical absorption through destructive interference, playing a central role in light-matter interaction and quantum information science. We report matter-wave induced transparency, where atomic collisional interactions induce transmission through a lossy molecular potential for the incident atomic scattering waves. Using cesium Bose-Einstein condensates and modulation-induced Feshbach resonances, we realize a three-level atom-molecule coupled system with unprecedented flexibility. Under the dark state condition, a narrow and tunable transparency window appears within a broad dissipative collisional resonance. The transparency window linewidth is controlled by modulation-induced coupling. And scattering pathways are selectable via multifrequency Floquet modulation. These results establish an interference-based route for exploring programmable nonequilibrium and non-Hermitian physics, steering quantum chemistry and precision measurements. △ Less

Submitted 6 July, 2026; v1 submitted 4 July, 2026; originally announced July 2026.

Comments: 8 pages, 5 figures

Gregory Nested Picard Iteration Schemes for Open Quantum Systems Governed by the Lindblad Equation

Authors: Jiuhua Hu, Daniel Appelo, Yingda Cheng

Abstract: Numerical simulation of quantum computing hardware and open quantum systems governed by the Lindblad equation is challenging due to the high dimensionality of the density matrix and the need to preserve fundamental physical properties. In our previous work, we developed an arbitrary-order, low-rank, completely positive and trace preserving (CPTP) method for the Lindblad equation with time-dependen… ▽ More Numerical simulation of quantum computing hardware and open quantum systems governed by the Lindblad equation is challenging due to the high dimensionality of the density matrix and the need to preserve fundamental physical properties. In our previous work, we developed an arbitrary-order, low-rank, completely positive and trace preserving (CPTP) method for the Lindblad equation with time-dependent Hamiltonians by nested Picard iteration (NPI). In this work, we develop Gregory NPI schemes, which are CPTP schemes constructed by Gregory-type quadrature on equispaced nodes. The methods, which are of order up to nine, substantially reduce the computational cost compared to our previously proposed NPI schemes with Gaussian quadrature rules, while retaining high-order accuracy and structure preservation. We analyze the stability of the resulting scheme for a physics-based test equation. Numerical experiments verify the convergence of the method and demonstrate the effectiveness of the low-rank approximation. We study the performance of a previously constructed CNOT gate for both closed and open quantum systems. △ Less

Submitted 27 June, 2026; originally announced June 2026.

MSC Class: 65L99; % Numerical methods for ordinary differential equations 15A69; % Multilinear algebra; tensor calculus 81Q99 65L99; 15A69; 81Q99

Single-sideband-interference twin-field quantum key distribution without global phase locking

Authors: Xingjian Li, Bingkun Wang, Jianyong Hu, Jianqiang Liu, Shuxiao Wu, Guosheng Feng, Zhixing Qiao, Changgang Yang, Ruiyun Chen, Chengbing Qin, Guofeng Zhang, Liantuan Xiao, Suotang Jia

Abstract: Twin-field quantum key distribution (TF QKD) can overcome the fundamental rate loss limit of repeaterless quantum links, but its practical deployment has long been hindered by the requirement of global phase locking between two independent lasers. By revisiting the fundamental principles of optical interference, this work reveals that interference in TF QKD inherently relies only on the instantane… ▽ More Twin-field quantum key distribution (TF QKD) can overcome the fundamental rate loss limit of repeaterless quantum links, but its practical deployment has long been hindered by the requirement of global phase locking between two independent lasers. By revisiting the fundamental principles of optical interference, this work reveals that interference in TF QKD inherently relies only on the instantaneous phase alignment of two independent optical pulses at the moment they temporally overlap, rather than on continuous global phase synchronization. Guided by this insight, we propose and demonstrate a single-sideband-interference TF-QKD protocol that eliminates global phase locking. Each user employs an IQ modulator to generate a weak single sideband as the quantum signal, while the intrinsically phase-correlated optical carrier propagates as a real-time phase reference. Carrier interference at the receiver enables real-time phase extraction and feedback compensation for the sidebands. Unlike prior no phase locking approaches requiring second- or microsecond-level coherence, in principle, our scheme reduces this requirement to nanoseconds. We achieve 98% interference visibility over 100.8 km fibre and secure key rates surpassing the PLOB bound in the high-loss regime, providing a simpler route towards practical long-distance quantum communication networks. △ Less

Submitted 26 June, 2026; originally announced June 2026.

Doppler-enhanced superheterodyne Rydberg microwave receiver

Authors: Yuwen Yin, Ruimin Chen, Shibing Ji, Jinlian Hu, Shaofeng Wang, Yunhui He, Jingxu Bai, Xiao-Qiang Shao, Yuechun Jiao, Jianming Zhao

Abstract: We report the enhanced sensitivity of the Rydberg microwave (MW) receiver by exploiting the Doppler effect in a vapor cell. A two-photon Rydberg ladder scheme is implemented via the co-propagation of probe and coupling lasers, which enhances the Doppler effect. When an MW field is applied, microwave dressing modifies the velocity-dependent resonance condition, enabling stronger contributions from… ▽ More We report the enhanced sensitivity of the Rydberg microwave (MW) receiver by exploiting the Doppler effect in a vapor cell. A two-photon Rydberg ladder scheme is implemented via the co-propagation of probe and coupling lasers, which enhances the Doppler effect. When an MW field is applied, microwave dressing modifies the velocity-dependent resonance condition, enabling stronger contributions from atoms with non-zero velocities and leading to an enhancement of the EIT transmission. Based on this mechanism, we achieve a sensitivity of $35.1\ \mathrm{nV\ cm^{-1}\ Hz^{-1/2}}$ using the heterodyne technique, which is 1.5 times better than that obtained in the counter-propagating configuration. Meanwhile, the required local oscillator (LO) field is reduced by a factor of 17.6 compared with the counter-propagating configuration, which is advantageous for applications requiring minimal radiation and low power consumption. Moreover, the co-propagating configuration is more amenable to integration or portable sensing platforms because multiple laser fields can be delivered through a single optical fiber. △ Less

Submitted 23 June, 2026; originally announced June 2026.

Comments: 6pages, 3 figures

Report number: Appl. Phys. Lett. 129, 014003 (2026)

Journal ref: Applied Physics Letters, 2026

Probing the Circular Unruh Effect with Cavity-Controlled Lamb Shifts

Authors: Yan Peng, Jiawei Hu, Hongwei Yu

Abstract: The Unruh effect predicts that accelerated observers perceive the inertial vacuum as populated by particles, providing a flat-spacetime analogue of Hawking radiation. Its direct observation, however, remains experimentally challenging, since an Unruh temperature of $1\,\mathrm{K}$ requires accelerations of order $10^{20}\,\mathrm{m/s^2}$. Here, we show that the Lamb shift of a centripetally accele… ▽ More The Unruh effect predicts that accelerated observers perceive the inertial vacuum as populated by particles, providing a flat-spacetime analogue of Hawking radiation. Its direct observation, however, remains experimentally challenging, since an Unruh temperature of $1\,\mathrm{K}$ requires accelerations of order $10^{20}\,\mathrm{m/s^2}$. Here, we show that the Lamb shift of a centripetally accelerated atom inside a high-$Q$ cavity provides a sensitive spectroscopic probe of the Unruh effect at dramatically lower accelerations. The cavity reshapes the electromagnetic density of states and converts otherwise tiny noninertial corrections into tunable level shifts. Depending on the atomic angular velocity and cavity detuning, the Lamb shift can be enhanced, strongly quenched, or completely screened. Remarkably, for experimentally realistic parameters, a rotation-induced shift of order $10\;\mathrm{Hz}$ can arise already at accelerations as low as $0.5\,\mathrm{m/s^2}$, more than twenty orders of magnitude below the acceleration scale conventionally associated with direct Unruh detection. These results identify cavity-controlled Lamb-shift spectroscopy as a viable route toward laboratory tests of the circular Unruh effect in the ultralow-acceleration regime. △ Less

Submitted 18 June, 2026; originally announced June 2026.

Experimental Characterization and Modeling of Measurement-Induced State-Transitions in a Fluxonium Superconducting Qubit

Authors: Martijn F. S. Zwanenburg, Jinlun Hu, Eugene Y. Huang, Figen Yilmaz, Siddharth Singh, Christian Kraglund Andersen

Abstract: Superconducting qubits are most often measured using dispersive readout, which, ideally, implements a projective quantum non-demolition (QND) measurement. While a larger readout drive can increase the signal and, thus, reduce discrimination errors in the readout, strong microwave drives may also cause non-QND errors by driving the qubit to a state outside the computational subspace. In this work,… ▽ More Superconducting qubits are most often measured using dispersive readout, which, ideally, implements a projective quantum non-demolition (QND) measurement. While a larger readout drive can increase the signal and, thus, reduce discrimination errors in the readout, strong microwave drives may also cause non-QND errors by driving the qubit to a state outside the computational subspace. In this work, we experimentally characterize measurement-induced state transitions (MIST) in a fluxonium qubit over its full external flux range. We further numerically calculate the MIST errors, and find that the theory accurately predicts eleven experimentally identified regions with increased MIST. In addition to transitions to higher fluxonium levels, we also find that, at certain flux points, MIST errors are dominated by transitions that include the transmission-line-like array modes of the fluxonium's superinductor. The excellent match between theory and experiment validates that the models accurately predict the occurrence of MIST in these systems, and further highlights the influence of array modes in fluxonium readout. △ Less

Submitted 16 June, 2026; originally announced June 2026.

Comments: 11 pages, 6 figures

Acceleration-induced spectral blind spots in stimulated atomic transitions

Authors: Jiawei Hu, Hongwei Yu

Abstract: Stimulated transitions are among the most fundamental processes in light-matter interaction, underlying resonant absorption and emission in atomic systems. Here we show that uniform acceleration can convert this familiar response into a frequency-selective absence of response. Specifically, when an incident photon has a nonzero momentum component transverse to the acceleration, the stimulated tran… ▽ More Stimulated transitions are among the most fundamental processes in light-matter interaction, underlying resonant absorption and emission in atomic systems. Here we show that uniform acceleration can convert this familiar response into a frequency-selective absence of response. Specifically, when an incident photon has a nonzero momentum component transverse to the acceleration, the stimulated transition probability vanishes at a discrete set of frequencies fixed by the acceleration, the atomic transition frequency, and the photon propagation angle. At these spectral blind spots, both ordinary stimulated absorption and acceleration-induced excitation are simultaneously suppressed, rendering the atom effectively unresponsive to the incident radiation. The effect arises from the nontrivial response of accelerated atoms to quantum vacuum fluctuations and provides a distinctive signature of the Unruh effect through the absence, rather than the enhancement, of stimulated transitions. We further provide an order-of-magnitude estimate showing that an electron-based implementation with spin splitting in combined electric and magnetic fields could access the required parameter regime. These results reveal an unexplored form of acceleration-modified light-matter interaction and identify spectral blind spots as a new manifestation of the Unruh effect. △ Less

Submitted 15 June, 2026; originally announced June 2026.

Comments: 5 pages, 1 figure

Improved Cryogenic Photodiode Optical Biasing for Low-Noise and Low-Jitter Superconducting Nanowire Single-Photon Detectors

Authors: Jia-Hao Hu, Wei-Jun Zhang, Wen-Shuo Yu, Yu-Ze Wang, Dong-Wei Chu, Ya-Tao Peng, Hui-Qin Yu, Pu-Sheng Yuan, Ling Wu, Li-Xing You

Abstract: We experimentally demonstrate an improved optical biasing scheme for superconducting nanowire single-photon detectors (SNSPDs), which employs a cryogenic InGaAs-InP photodiode (PD) as a local bias source. It is found that, under illumination from a stable external light source, this PD generates a stable photocurrent in a cryogenic environment (~2.3 K), with fluctuations in the photocurrent primar… ▽ More We experimentally demonstrate an improved optical biasing scheme for superconducting nanowire single-photon detectors (SNSPDs), which employs a cryogenic InGaAs-InP photodiode (PD) as a local bias source. It is found that, under illumination from a stable external light source, this PD generates a stable photocurrent in a cryogenic environment (~2.3 K), with fluctuations in the photocurrent primarily attributed to fluctuations in the incident optical power. Furthermore, by screening and effectively blocking stray photons leaking from the PD, which give rise to background dark counts, we have achieved an SNSPD exhibiting an ultra-low intrinsic dark count rate of 1e-4 cps. Utilizing this improved optical biasing technique, our SNSPD achieved performance comparable to that obtained under conventional electrical biasing: a system detection efficiency of 80.7%, a background dark count rate of 32.6 cps, and a minimum timing jitter of 57.5 ps. These results indicate that cryogenic-PD-based optical biasing serves as a viable, low-noise, and low-jitter alternative to traditional electrical biasing. Moreover, this work offers useful design guidance for the future development of PD-based low-noise bias sources and for the construction of all-photonic SNSPD systems tailored for high-precision quantum photonics applications. △ Less

Submitted 14 June, 2026; v1 submitted 5 June, 2026; originally announced June 2026.

Comments: 12 pages, 5 figures

Training-Free Quantum Generative Paradigm via Local Parent Hamiltonians

Authors: Shu Tian, Jiaqi Hu, Rebing Wu, Yu Shi

Abstract: We propose a training-free quantum generative paradigm, which is fundamentally different from current generative models, which demand substantial computational power, face practical scalability limits, and often function as opaque black boxes, despite their remarkable success. We enable image and text generation without parameter training, by constructing a local parent Hamiltonian whose ground st… ▽ More We propose a training-free quantum generative paradigm, which is fundamentally different from current generative models, which demand substantial computational power, face practical scalability limits, and often function as opaque black boxes, despite their remarkable success. We enable image and text generation without parameter training, by constructing a local parent Hamiltonian whose ground state encodes the target distribution and then solving the global Hamiltonian. Rooted directly in quantum mechanical principles, this approach establishes a new pathway for generative modeling that leverages superposition and entanglement to maintain global consistency. △ Less

Submitted 25 May, 2026; originally announced May 2026.

Comments: 8 pages

Generalized Shift Vector as the Intrinsic Dipole of Many-Body Correlated Electronic States

Authors: Jiaming Hu, Sudipta Kundu, Zhichao Guo, Joshua J. P. Thompson, Wenbin Li, Hua Wang, Bartomeu Monserrat

Abstract: Shift vectors play a central role in nonlinear optics and transport phenomena, where they are usually understood as charge-center shifts associated with transitions between quantum states. Here we show that the same geometric structure can be more fundamentally understood as the intrinsic dipole moment of a single correlated state. Our derivation clarifies the local and global aspects of gauge inv… ▽ More Shift vectors play a central role in nonlinear optics and transport phenomena, where they are usually understood as charge-center shifts associated with transitions between quantum states. Here we show that the same geometric structure can be more fundamentally understood as the intrinsic dipole moment of a single correlated state. Our derivation clarifies the local and global aspects of gauge invariance, the origin of the phase-gradient term, and its connection to the internal coherence structure of many-body correlations. The single-state shift character appears both as a displacement of the real-space joint probability density and as a linear electric-field modification in energy space. Applying this framework to optically induced correlations, electron-phonon-mediated processes, and excitonic electron-hole states, we recover previously proposed shift vectors and the standard expression for the shift current as special cases. Our results establish a common physical foundation for shift vectors as intrinsic dipolar properties of correlated electronic states. △ Less

Submitted 7 June, 2026; v1 submitted 22 May, 2026; originally announced May 2026.

Comments: 17 pages, 2 figures

Quantum compressed sensing

Authors: Jianyong Hu, Wei Li, Shuxiao Wu, Liwen Zhang, Yongchuang Sun, Jiazhao Tian, Guosheng Feng, Zhixing Qiao, Jianqiang Liu, Changgang Yang, Ruiyun Chen, Chengbing Qin, Guofeng Zhang, Liantuan Xiao, Suotang Jia

Abstract: How many measurements are fundamentally required to capture a signal. Shannon's information theory established the bedrock of this question in 1948, the Nyquist Shannon theorem set the first answer, and compressed sensing (CS) rewrote it in 2006 by reducing the required measurement number to M = O(Klog(N/K)) for a K sparse signal. Here, we propose quantum compressed sensing (QCS), a paradigm that… ▽ More How many measurements are fundamentally required to capture a signal. Shannon's information theory established the bedrock of this question in 1948, the Nyquist Shannon theorem set the first answer, and compressed sensing (CS) rewrote it in 2006 by reducing the required measurement number to M = O(Klog(N/K)) for a K sparse signal. Here, we propose quantum compressed sensing (QCS), a paradigm that reframes signal acquisition as a unitary quantum evolution. By encoding high dimensional signal information into a single quantum probe state, then introducing domain-alignment evolution,a physically realizable unitary transformation that maps the sparse basis directly onto the measurement basis. QCS executes the support-set search at the quantum level without consuming measurement trials. The logarithmic penalty vanishes, compressing the required measurement number from the classical bound to M =O(K) and reducing reconstruction from ill posed optimization to linear estimation. We experimentally validate QCS using frequency and time domain sparse signals, confirming that the measurement number scales linearly with sparsity and decouples entirely from the signal dimension. Our work provides a physical pathway toward ultimate information acquisition efficiency, with broad implications for sensing, imaging, and communication. △ Less

Submitted 15 May, 2026; originally announced May 2026.

Graduate Training in Quantum Information Science and Engineering: Lessons, Challenges, and a Roadmap from the NSF Research Traineeship Programs

Authors: Yohannes Abate, Victor Acosta, Alessandro Alabastri, Mehmet Aydeniz, Viktoriia E. Babicheva, Lincoln D. Carr, I-Tung Chen, Wandi Ding, Tara Drake, Mattias Fitzpatrick, Kai-Mei C. Fu, Jay Gupta, Kaden R. A. Hazzard, Sophia E. Hayes, Jin Hu, Hilary M. Hurst, Sohrab Ismail-Beigi, Ehsan Khatami, Junichiro Kono, Cheng-Yu Lai, Xiuling Li, Yingmei Liu, Sara Mouradian, Kater Murch, Borja Peropadre , et al. (9 additional authors not shown)

Abstract: Since 2019, eighteen NSF Research Traineeship (NRT) awards in quantum information science and engineering (QISE) and adjacent fields have been funded, constituting the largest NSF-coordinated investment in graduate QISE training in the United States. Synthesizing lessons from our programs, we work through the central tensions that every QISE graduate program must negotiate: between depth in a home… ▽ More Since 2019, eighteen NSF Research Traineeship (NRT) awards in quantum information science and engineering (QISE) and adjacent fields have been funded, constituting the largest NSF-coordinated investment in graduate QISE training in the United States. Synthesizing lessons from our programs, we work through the central tensions that every QISE graduate program must negotiate: between depth in a home discipline and breadth across the field, between structured instruction and open-ended experiential and hands-on learning, and between training individual specialists and cultivating teams that collectively cover all areas of QISE. We describe the structural and pedagogical innovations the NRT programs have developed in response, assess what is working and what remains unresolved, and sketch 12 open problems the community will need to address as QISE graduate education scales beyond the well-resourced research universities where it has up till now been mainly concentrated. Eight concrete recommendations follow: (1) adopt the startup model of team-based training as an organizing philosophy; (2) invest immediately in sensing and communication curriculum development; (3) build student agency into program governance, not just activities; (4) establish structural mechanisms for industrial engagement rather than depending on goodwill; (5) design for sustainability from year one; (6) develop graduate-level textbooks spanning all three QISE pillars: computing, sensing, and communications; (7) establish shared outcome assessment instruments across programs; and (8) develop structured mechanisms for faculty professional development in QISE. △ Less

Submitted 8 May, 2026; originally announced May 2026.

Comments: 49 pages, 3 figures, 1 table

Quantum Grover Adaptive Search for Discrete Simulation Optimization

Authors: Mingjie Hu, Jian-qiang Hu, Enlu Zhou

Abstract: Quantum computing has advanced rapidly in recent years and has shown advantages in a variety of domains. In this paper, we investigate its potential for discrete simulation optimization in the fixed-confidence setting, a fundamental problem in the simulation literature. We first introduce a quantum simulation oracle that prepares a coherent superposition over all candidate solutions and provides t… ▽ More Quantum computing has advanced rapidly in recent years and has shown advantages in a variety of domains. In this paper, we investigate its potential for discrete simulation optimization in the fixed-confidence setting, a fundamental problem in the simulation literature. We first introduce a quantum simulation oracle that prepares a coherent superposition over all candidate solutions and provides the foundation for quantum algorithm design. Based on this oracle, we develop the first Grover-search-based quantum algorithm for discrete simulation optimization, called SOGAS. In particular, SOGAS uses a binary-search framework to progressively eliminate suboptimal solutions while carefully controlling the error probability, and eventually identifies a set of near-optimal solutions. We prove that SOGAS returns a near-optimal solution with probability at least the prescribed confidence level and achieves a quadratic speedup in the dependence of query complexity on the number of candidate solutions. Numerical experiments further show that SOGAS substantially outperforms classical benchmarks and provide empirical evidence for quantum advantage in discrete simulation optimization. △ Less

Submitted 29 April, 2026; originally announced April 2026.

Quantum Compressed Sensing Enables Image Classification with a Single Photon

Authors: Yanshan Fan, Jianyong Hu, Shuxiao Wu, Zhixing Qiao, Guosheng Feng, Changgang Yang, Jianqiang Liu, Ruiyun Chen, Chengbing Qin, Guofeng Zhang, Liantuan Xiao, Suotang Jia

Abstract: Image classification is a core task of intelligent sensing, conventionally follows a sequential imaging then processing pipeline. However, redundant high-dimensional image reconstruction is inherently inefficient, especially in photon limited scenarios. Here we report a photon level image classification method using quantum compressed sensing, which reformulates the classification task as a sparse… ▽ More Image classification is a core task of intelligent sensing, conventionally follows a sequential imaging then processing pipeline. However, redundant high-dimensional image reconstruction is inherently inefficient, especially in photon limited scenarios. Here we report a photon level image classification method using quantum compressed sensing, which reformulates the classification task as a sparse signal measurement problem directly oriented toward class labels. By exploiting the parallelism of photonic quantum superposition states, a single photon can be encoded the complete spatial information of a high-dimensional image. Through a diffractive deep neural network, we physically construct a dedicated measurement basis aligned with the class space, enabling signal-dependent adaptive compressive measurement. Ideally, our method can extract class information via a single quantum projective measurement, reducing the required number of measurements from the logarithmic scaling O(Klog(N/K)) of classical compressed sensing to the constant-order information-theoretic limit M = K = 1. Experimental results show that a classification accuracy of 69.0% can be achieved by using a single-photon detection event as the decision criterion, while it increases to 95.0% with four-photon detection events. This work demonstrates image classification at the energy efficiency limit and introduces a measurement as decision framework. It provides a foundation for intelligent sensing systems that operate under extreme photon budgets and harsh environments. △ Less

Submitted 28 April, 2026; originally announced April 2026.

Crosstalk-robust superconducting two-qubit geometric gates using tunable couplers

Authors: Bo-Xun Deng, Jia-Qi Hu, Cheng-Yun Ding, Zheng-Yuan Xue, Tao Chen

Abstract: The design of coupler-based superconducting two-qubit gates simplifies circuit layout and alleviate frequency crowding, thereby enhancing the scalability and flexibility of quantum chips. However, in such architectures, a trade-off often exists between suppressing crosstalk and reducing gate duration, and how to achieve synergistic optimization of both remains an open challenge. To address this, t… ▽ More The design of coupler-based superconducting two-qubit gates simplifies circuit layout and alleviate frequency crowding, thereby enhancing the scalability and flexibility of quantum chips. However, in such architectures, a trade-off often exists between suppressing crosstalk and reducing gate duration, and how to achieve synergistic optimization of both remains an open challenge. To address this, this paper proposes a coupler-assisted superconducting two-qubit geometric gate scheme oriented towards crosstalk robustness. By introducing additional parametric degrees of freedom, the scheme steers the system evolution along desired trajectories, thereby flexibly avoiding crosstalk-sensitive operational regions. Numerical simulations demonstrate that the proposed scheme can effectively suppress crosstalk errors while enabling fast gate operations, and exhibits strong robustness against typical experimental imperfections such as qubit frequency drift. Moreover, even when accounting for unavoidable high-frequency oscillation terms and qubit decoherence in realistic physical systems, our crosstalk-robust two-qubit geometric gates still achieve high fidelity. This work provides a feasible pathway toward robust and efficient two-qubit gate implementation in superconducting quantum computation. △ Less

Submitted 9 April, 2026; originally announced April 2026.

Comments: 11 pages, 5 figures

Post-Selection-Free Decoding of Measurement-Induced Area-Law Phases via Neural Networks

Authors: Hui Yu, Jiangping Hu, Shi-Xin Zhang

Abstract: Monitored quantum circuits host a rich variety of exotic non-equilibrium phases. Among the most representative examples are measurement-induced phase transitions between distinct area-law entangled states. However, because these transitions are characterized by specific entanglement quantities such as mutual information or topological entanglement entropy that are nonlinear functionals of the dens… ▽ More Monitored quantum circuits host a rich variety of exotic non-equilibrium phases. Among the most representative examples are measurement-induced phase transitions between distinct area-law entangled states. However, because these transitions are characterized by specific entanglement quantities such as mutual information or topological entanglement entropy that are nonlinear functionals of the density matrix, their experimental observation requires multiple identical quantum trajectories via post-selection, which becomes exponentially unfeasible for large systems. Here, we leverage modern machine learning tools to address this challenge. We devise a neural network architecture combining a convolutional neural network with an attention mechanism, and use raw measurement outcomes directly as input to classify trivial, long-range entangled, and symmetry-protected topological phases. We show that the system's relaxation to a steady-state phase manifests as a sharp convergence in the classifier's accuracy, entirely bypassing the need for quantum state reconstruction. We systematically study the performance of our network as a function of sample size, input data, spatial and temporal constraints, and system size scalability. Our results demonstrate that this approach is robust and post-selection free, offering a practical pathway for experimentally probing measurement-induced phases. △ Less

Submitted 3 April, 2026; originally announced April 2026.

Comments: 9 pages,5 figures

Quantum gravitodiamagnetic interaction

Authors: Di Hao, Jiawei Hu, Hongwei Yu

Abstract: In the framework of linearized quantum gravity, we investigate the quantum gravitational interaction induced by the gravitodiamagnetic coupling of two massive objects to vacuum fluctuations of the gravitational field. Starting from the Lagrangian of a particle in a gravitational field and employing the formalism of Weyl gravitoelectromagnetism, we derive the interaction Hamiltonian associated with… ▽ More In the framework of linearized quantum gravity, we investigate the quantum gravitational interaction induced by the gravitodiamagnetic coupling of two massive objects to vacuum fluctuations of the gravitational field. Starting from the Lagrangian of a particle in a gravitational field and employing the formalism of Weyl gravitoelectromagnetism, we derive the interaction Hamiltonian associated with gravitodiamagnetic coupling. Unlike the linear couplings that arise in gravitoelectric and gravitomagnetic interactions, the gravitodiamagnetic coupling depends quadratically on the gravitomagnetic field. Based on this Hamiltonian, we show that, for a spherically symmetric gravitational hydrogen-like system in its ground state, the induced quadrupole moment has the opposite sign to the applied gravitomagnetic field, which is the defining signature of gravitodiamagnetism. Using leading-order perturbation theory, we further obtain an explicit expression for the resulting interaction potential, which is attractive and scales as $r^{-11}$ at all separations, where $r$ denotes the distance between the two objects. △ Less

Submitted 28 March, 2026; originally announced March 2026.

Comments: 21 pages, 1 figure

Achieving double-logarithmic precision dependence in optimization-based quantum unstructured search

Authors: Zhijian Lai, Dong An, Jiang Hu, Zaiwen Wen

Abstract: Grover's algorithm is a fundamental quantum algorithm that achieves a quadratic speedup for unstructured search problems of size $N$. Recent studies have reformulated this task as a maximization problem on the unitary manifold and solved it via linearly convergent Riemannian gradient ascent (RGA) methods, resulting in a complexity of $O(\sqrt{N/M}\log (1/\varepsilon))$, where $M$ denotes the numbe… ▽ More Grover's algorithm is a fundamental quantum algorithm that achieves a quadratic speedup for unstructured search problems of size $N$. Recent studies have reformulated this task as a maximization problem on the unitary manifold and solved it via linearly convergent Riemannian gradient ascent (RGA) methods, resulting in a complexity of $O(\sqrt{N/M}\log (1/\varepsilon))$, where $M$ denotes the number of target items and $\varepsilon$ denotes the success probability error. In this work, we adopt the Riemannian modified Newton (RMN) method to solve the quantum search problem, under the assumption that the ratio $ M/N$ is known. We show that, in this setting, the Riemannian Newton direction is collinear with the Riemannian gradient in the sense that the Riemannian gradient is always an eigenvector of the corresponding Riemannian Hessian. This structure removes the overhead of Hessian inversion and allows the proposed RMN method to retain the local quadratic convergence in terms of the error $\varepsilon$. More precisely, we rigorously prove an overall complexity of $O(\sqrt{N/M}+\log\log(1/\varepsilon))$. Furthermore, our approach remains Grover-compatible, namely, it relies exclusively on the standard Grover diffusion and oracle operators to ensure algorithmic implementability, and its parameter update process can be efficiently precomputed on classical computers. △ Less

Submitted 15 June, 2026; v1 submitted 26 March, 2026; originally announced March 2026.

MSC Class: 81P68; 90C26; 65K10 ACM Class: F.2.2; G.1.6

Stabilizing correlated pair tunneling of spin-orbit-coupled bosons in a non-Hermitian driven double well

Authors: Miaoqian Lu, Xinzhou Guan, Mohan Xia, Wenjuan Li, Jincheng Hu, Xinyue Zhang, Yunrong Luo

Abstract: We present an analytical framework for stabilizing second-order correlated tunneling of two spin-orbit-coupled bosons in a periodically driven non-Hermitian double-well potential. By combining Floquet theory with multiple-scale asymptotic analysis, we derive effective second-order dynamics and exact quasienergy spectra in the strongly interacting regime. Our analysis reveals distinct stability mec… ▽ More We present an analytical framework for stabilizing second-order correlated tunneling of two spin-orbit-coupled bosons in a periodically driven non-Hermitian double-well potential. By combining Floquet theory with multiple-scale asymptotic analysis, we derive effective second-order dynamics and exact quasienergy spectra in the strongly interacting regime. Our analysis reveals distinct stability mechanisms for three fundamental tunneling channels: interwell spin-conserving, interwell spin-flipping, and intrawell spin-flipping. For balanced gain and loss, we identify discrete, well-defined parameter regions where stable pair tunneling emerges, with the spin-flipping channel exhibiting a characteristic symmetry absent in its spin-conserving counterpart. Under unbalanced gain-loss conditions, stability is achieved only when the gain and loss coefficients satisfy specific parametric relations, enabling dissipation-controlled tunneling. Most notably, stable intrawell spin-flipping, while inherently unstable for an initial Fock state, becomes accessible when the system is prepared in a coherent superposition state, thereby revealing that initial-state coherence can serve as a control parameter for dynamical stability in non-Hermitian systems. These results expand the possibilities for controlling correlated tunneling in many-body systems with engineered dissipation. △ Less

Submitted 26 March, 2026; v1 submitted 18 March, 2026; originally announced March 2026.

Macroscopic entanglement distribution with atomic ensembles

Authors: Shuang Li, Jin Hu, Ilia D. Lazarev, Jonathan Raghoonanan, Valentin Ivannikov, Alexey N. Pyrkov, Tim Byrnes

Abstract: The distribution of entanglement is a crucial task for quantum communication towards realizing a globe-spanning quantum internet. Recently a protocol for deterministic long-distance distribution of macroscopic entanglement over a network of ensembles of qubits was introduced [Adv. Quantum Technol. 2025, 8, 2400524]. It was shown that this protocol allows for the propagation of macroscopic amounts… ▽ More The distribution of entanglement is a crucial task for quantum communication towards realizing a globe-spanning quantum internet. Recently a protocol for deterministic long-distance distribution of macroscopic entanglement over a network of ensembles of qubits was introduced [Adv. Quantum Technol. 2025, 8, 2400524]. It was shown that this protocol allows for the propagation of macroscopic amounts of entanglement with a protocol complexity that is independent on the ensemble size. However, questions remained on whether the scheme is viable, particularly for a large particle number, which is the case for realistic atomic ensembles. Here we develop improved numerical techniques that allow calculation of realistic ensemble sizes up to 10^6 with a negligible loss of accuracy. We find that moderate dephasing leaves the entanglement largely intact at the magic times, whereas stronger noise monotonically suppresses the entanglement. Our results demonstrate that the protocol retains its functionality towards the macroscopic regime and provides quantitative benchmarks for its robustness under a realistic level of decoherence. △ Less

Submitted 6 March, 2026; originally announced March 2026.

Significant modifications of Lamb shift at small centripetal accelerations

Authors: Yan Peng, Jiawei Hu, Hongwei Yu

Abstract: We investigate the Lamb shift of centripetally accelerated atoms coupled to electromagnetic vacuum fluctuations. Focusing on a very small orbital radius (so that the tangential speed remains nonrelativistic and the proper centripetal acceleration can be extremely small), we show that the resulting level shift is intrinsically anisotropic and depends sensitively on the atomic polarization direction… ▽ More We investigate the Lamb shift of centripetally accelerated atoms coupled to electromagnetic vacuum fluctuations. Focusing on a very small orbital radius (so that the tangential speed remains nonrelativistic and the proper centripetal acceleration can be extremely small), we show that the resulting level shift is intrinsically anisotropic and depends sensitively on the atomic polarization direction. For atoms polarizable along the rotation axis, the leading noninertial contribution enters only at second order in the orbital radius and can slightly increase the energy-level spacing. For atoms polarizable perpendicular to the rotation axis, the noninertial contribution appears already at zeroth order in the radius and always increases the energy-level spacing. Remarkably, when the angular velocity greatly exceeds the transition frequency, the rotation-induced correction can become comparable in magnitude to the inertial Lamb shift, indicating that circular motion can significantly modify the Lamb shift even in the regime of very small centripetal accelerations. △ Less

Submitted 10 August, 2026; v1 submitted 6 March, 2026; originally announced March 2026.

Comments: 11 pages, 0 figure, published version

Journal ref: Phys. Rev. D 114, 045006 (2026)

Optical pumping of alkali-metal vapor in the quasi-high-pressure regime

Authors: Kezheng Yan, Jinbo Hu, Nan Zhao

Abstract: Optical pumping is fundamental to high-precision measurement using thermal alkali-metal atoms in vapor cells. In applications such as atomic magnetometry, buffer gases (e.g., $\mathrm{N}_2$ or $\mathrm{He}$) at specific pressures are introduced to quench fluorescence and mitigate wall relaxation. In the high-pressure limit (e.g., the $\mathrm{N}_2$ pressure $p_{\mathrm{N}_2}> 1$~atm), where collis… ▽ More Optical pumping is fundamental to high-precision measurement using thermal alkali-metal atoms in vapor cells. In applications such as atomic magnetometry, buffer gases (e.g., $\mathrm{N}_2$ or $\mathrm{He}$) at specific pressures are introduced to quench fluorescence and mitigate wall relaxation. In the high-pressure limit (e.g., the $\mathrm{N}_2$ pressure $p_{\mathrm{N}_2}> 1$~atm), where collisional broadening exceeds hyperfine splittings of the atoms, optical pumping theory provides a clear description of the angular momentum exchange between photons and atomic spins. However, in many magnetic sensing scenarios, the high-pressure approximation becomes inadequate as its pressure conditions are not strictly satisfied. Consequently, an explicit description of optical pumping under realistic pressures is critical for selecting operating points and enhancing system performance. To address this, we develop a unified theoretical framework of optical pumping in the quasi-high-pressure regime, where collisional broadening is comparable to the ground-state hyperfine splitting. We demonstrate that light absorption, spin polarization, and magnetic-resonance linewidth in this regime differ significantly from those predicted by the high-pressure limit and offer favorable operating conditions. Our study extends conventional modeling and offers critical guidance for atomic magnetometry operating under realistic buffer gas pressures. △ Less

Submitted 11 May, 2026; v1 submitted 5 March, 2026; originally announced March 2026.

Comments: 15 pages, 10 figures

Entanglement dynamics for atoms near a reflecting boundary: Enhancement and suppression by environment-induced interactions

Authors: Ying Chen, Hongwei Yu, Jiawei Hu

Abstract: We investigate how environment-induced interactions influence the entanglement dynamics of two atoms held at fixed positions near a perfectly reflecting boundary. Within the framework of open quantum systems, we explicitly incorporate the environment-induced energy shifts, including both atom-boundary contributions and an environment-induced atom-atom interaction, which are often neglected in prev… ▽ More We investigate how environment-induced interactions influence the entanglement dynamics of two atoms held at fixed positions near a perfectly reflecting boundary. Within the framework of open quantum systems, we explicitly incorporate the environment-induced energy shifts, including both atom-boundary contributions and an environment-induced atom-atom interaction, which are often neglected in previous studies. We show that, for any initial two-atom state, these energy-shift effects qualitatively and quantitatively modify the entanglement dynamics relative to treatments that omit them. Depending on the geometry and parameter regime, the environment-induced interactions can either enhance entanglement generation -- yielding a larger maximum concurrence and a longer entanglement lifetime -- or suppress it, reducing both the peak concurrence and the survival time. This behavior contrasts sharply with the free-space case, where the environment-induced atom-atom interaction affects entanglement generation only for a restricted class of initial states and does so in an exclusively assisting manner. △ Less

Submitted 15 June, 2026; v1 submitted 27 February, 2026; originally announced February 2026.

Comments: 10 pages, 4 figures

Journal ref: Phys. Rev. A 113, 062437 (2026)

Superresolution technique beyond the diffraction limit under a structured beam via different optical nanostructures

Authors: Subhankar Roy, Jianping Hu, M Ummal Momeen

Abstract: To overcome the limit of diffraction while achieving the superresolution technique, solid immersion lenses are the key optical elements for data storage and nanophotonics applications. Recent demonstrations have shown how different nanostructures (such as elliptical solid immersion lenses) are used in diverse fields of increasing resolution in the presence of a structured Gaussian beam. By applyin… ▽ More To overcome the limit of diffraction while achieving the superresolution technique, solid immersion lenses are the key optical elements for data storage and nanophotonics applications. Recent demonstrations have shown how different nanostructures (such as elliptical solid immersion lenses) are used in diverse fields of increasing resolution in the presence of a structured Gaussian beam. By applying twisted beams such as angular momentum beams (Laguerre- Gaussian) and spatial higher-order Gaussian beams (Hermite- Gauss), we can attain a sharp near-field focal spot pattern, which is considerably better than the conventional solid immersion lens structure in ~mm scale specifically for imaging beyond diffraction limit. Our computation results present a resolution of ~27 nm under a specific Hermite -Gauss mode illumination on a pyramidal shape nanolens structure. By numerical simulations, tolerance has been confirmed with a slight variation in beam size and geometrical modification to make the model compatible with fabrication errors. This narrow bandwidth intensity distribution can be utilized for scanning the sample with higher resolution, especially in the field of quantum technology. △ Less

Submitted 15 June, 2026; v1 submitted 22 February, 2026; originally announced February 2026.

Z2 Lattice Gauge Theory on Non-trivial Topology and Its Quantum Simulation

Authors: Jiaqi Hu, Shu Tian, Xiaopeng Cui, Rebing Wu, Man-Hong Yung, Yu Shi

Abstract: Wegner duality is essential for Z2 lattice gauge theory, yet the duality on non-trivial topologies has remained implicit. We extend Wegner duality to arbitrary topology and dimension, obtaining a new class of Ising models, in which topology is encoded in non-local domain-wall patterns. Without the overhead of gauge constraints, simulating this model on an L*L torus requires only L*L qubits with tw… ▽ More Wegner duality is essential for Z2 lattice gauge theory, yet the duality on non-trivial topologies has remained implicit. We extend Wegner duality to arbitrary topology and dimension, obtaining a new class of Ising models, in which topology is encoded in non-local domain-wall patterns. Without the overhead of gauge constraints, simulating this model on an L*L torus requires only L*L qubits with two-body couplings, halving the conventional four-body coupled 2L*L qubits, enabling full experimental realization of Z2 lattice gauge theory on near-term devices. △ Less

Submitted 23 January, 2026; originally announced January 2026.

Comments: 8 pages

Dynamical Spectral Function of the Kagome Quantum Spin Liquid

Authors: Jiahang Hu, Runze Chi, Yibin Guo, B. Normand, Hai-Jun Liao, T. Xiang

Abstract: Quantum spin liquids (QSLs) host exotic fractionalized magnetic and gauge-field excitations whose microscopic origins and experimental verification remain frustratingly elusive. In the absence of static magnetic order, the spin excitation spectrum constitutes the crucial probe of QSL behavior, but its theoretical computation is a serious challenge. Here we employ state-of-the-art tensor-network me… ▽ More Quantum spin liquids (QSLs) host exotic fractionalized magnetic and gauge-field excitations whose microscopic origins and experimental verification remain frustratingly elusive. In the absence of static magnetic order, the spin excitation spectrum constitutes the crucial probe of QSL behavior, but its theoretical computation is a serious challenge. Here we employ state-of-the-art tensor-network methods to obtain the full dynamical spectral function of the $J_1$-$J_2$ kagome Heisenberg model and benchmark our results by tracking their evolution across the magnetically ordered and QSL phases. Reducing $|J_2|/J_1$ causes increasingly strong spin-wave renormalization, flattening these modes then merging them into a continuum characteristic of deconfined spinons at all finite energies in the QSL. The low-energy continuum and the occurrence of gap closure at multiple high-symmetry points identify this gapless QSL as the U(1) Dirac spin liquid. These results establish a unified understanding of spin excitations in highly frustrated quantum magnets and provide clear spectral fingerprints for experimental detection in candidate kagome QSL materials. △ Less

Submitted 17 August, 2026; v1 submitted 21 December, 2025; originally announced December 2025.

Comments: 17 pages, 14 figures

Journal ref: Phys. Rev. Lett. 137, 076504 (2026)

A Grover-compatible manifold optimization algorithm for quantum search

Authors: Zhijian Lai, Dong An, Jiang Hu, Zaiwen Wen

Abstract: Grover's algorithm is a fundamental quantum algorithm that offers a quadratic speedup for the unstructured search problem by alternately applying physically implementable oracle and diffusion operators. In this paper, we reformulate the unstructured search as a maximization problem on the unitary manifold and solve it via the Riemannian gradient ascent (RGA) method. To overcome the difficulty that… ▽ More Grover's algorithm is a fundamental quantum algorithm that offers a quadratic speedup for the unstructured search problem by alternately applying physically implementable oracle and diffusion operators. In this paper, we reformulate the unstructured search as a maximization problem on the unitary manifold and solve it via the Riemannian gradient ascent (RGA) method. To overcome the difficulty that generic RGA updates do not, in general, correspond to physically implementable quantum operators, we introduce Grover-compatible retractions to restrict RGA updates to valid oracle and diffusion operators. Theoretically, we establish a local Riemannian $μ$-Polyak-Łojasiewicz (PL) inequality with $μ= \tfrac{1}{2}$, which yields a linear convergence rate of $1 - κ^{-1}$ toward the global solution. Here, the condition number $κ= L_{\mathrm{Rie}} / μ$, where $L_{\mathrm{Rie}}$ denotes the Riemannian Lipschitz constant of the gradient. Taking into account both the geometry of the unitary manifold and the special structure of the cost function, we show that $L_{\mathrm{Rie}} = O(\sqrt{N})$ for problem size $N = 2^n$. Consequently, the resulting iteration complexity is $O(\sqrt{N} \log(1/\varepsilon))$ for attaining an $\varepsilon$-accurate solution, which matches the quadratic speedup of $O(\sqrt{N})$ achieved by Grover's algorithm. These results demonstrate that an optimization-based viewpoint can offer fresh conceptual insights and lead to new advances in the design of quantum algorithms. △ Less

Submitted 9 June, 2026; v1 submitted 9 December, 2025; originally announced December 2025.

Comments: Newly added supplementary materials

MSC Class: 81P68; 90C26; 65K10

Arbitrary High Order Low-rank Completely Positive and Trace Preserving (CPTP) Schemes for Lindblad Equations with Time-dependent Hamiltonian

Authors: Jiuhua Hu, Daniel Appelo, Yingda Cheng

Abstract: In this paper, we develop a framework for designing arbitrary high order low-rank schemes for the Lindblad equation with time-dependent Hamiltonians. Our approach is based on nested Picard iterative integrators (NPI) and results in schemes in Kraus form that are completely positive and trace preserving (CPTP). The schemes are amenable to low rank formulations, making them suitable for problems whe… ▽ More In this paper, we develop a framework for designing arbitrary high order low-rank schemes for the Lindblad equation with time-dependent Hamiltonians. Our approach is based on nested Picard iterative integrators (NPI) and results in schemes in Kraus form that are completely positive and trace preserving (CPTP). The schemes are amenable to low rank formulations, making them suitable for problems where the matrix rank of the density matrix is small. △ Less

Submitted 14 November, 2025; originally announced November 2025.

A passive atomtronics filter for Fermi gases

Authors: Jun Hao Hue, Martin-Isbjörn Trappe, Piotr T. Grochowski, Jonathan Lau, Leong-Chuan Kwek

Abstract: We design an atomtronic filter device that spatially separates the components of a two-component Fermi gas with repulsive contact interactions in a two-dimensional geometry. With the aid of density--potential functional theory (DPFT), which can accurately simulate Fermi gases in realistic settings, we propose and characterize a barbell-shaped trapping potential, where a bridge-shaped potential con… ▽ More We design an atomtronic filter device that spatially separates the components of a two-component Fermi gas with repulsive contact interactions in a two-dimensional geometry. With the aid of density--potential functional theory (DPFT), which can accurately simulate Fermi gases in realistic settings, we propose and characterize a barbell-shaped trapping potential, where a bridge-shaped potential connects two ring-shaped potentials. In the strongly repulsive regime, each of the ring traps eventually stores one of the fermion species. Our simulations are a guide to designing component filters for initially mixed, weakly repulsive spin components. We demonstrate that the functioning of this barbell design is robust against variations in experimental settings, for example, across particle numbers, for small deformations of the trap geometry, or if interatomic interactions differ from the bare contact repulsion. Our investigation marks the first step in establishing DPFT as a comprehensive simulation framework for fermionic atomtronics. △ Less

Submitted 9 November, 2025; originally announced November 2025.

Comments: 9 pages, 8 figures

Quantum-coherent optical isolation and circulation using frequency conversion on a chip

Authors: Jierui Hu, Hao Yuan, Joshua Akin, Shanhui Fan, Kejie Fang

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 a… ▽ More 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. △ Less

Submitted 9 December, 2025; v1 submitted 1 November, 2025; originally announced November 2025.

HPC-Driven Modeling with ML-Based Surrogates for Magnon-Photon Dynamics in Hybrid Quantum Systems

Authors: Jialin Song, Yingheng Tang, Pu Ren, Shintaro Takayoshi, Saurabh Sawant, Yujie Zhu, Jia-Mian Hu, Andy Nonaka, Michael W. Mahoney, Benjamin Erichson, Zhi Yao

Abstract: Simulating hybrid magnonic quantum systems remains a challenge due to the large disparity between the timescales of the two systems. We present a massively parallel GPU-based simulation framework that enables fully coupled, large-scale modeling of on-chip magnon-photon circuits. Our approach resolves the dynamic interaction between ferromagnetic and electromagnetic fields with high spatiotemporal… ▽ More Simulating hybrid magnonic quantum systems remains a challenge due to the large disparity between the timescales of the two systems. We present a massively parallel GPU-based simulation framework that enables fully coupled, large-scale modeling of on-chip magnon-photon circuits. Our approach resolves the dynamic interaction between ferromagnetic and electromagnetic fields with high spatiotemporal fidelity. To accelerate design workflows, we develop a physics-informed machine learning surrogate trained on the simulation data, reducing computational cost while maintaining accuracy. This combined approach reveals real-time energy exchange dynamics and reproduces key phenomena such as anti-crossing behavior and the suppression of ferromagnetic resonance under strong electromagnetic fields. By addressing the multiscale and multiphysics challenges in magnon-photon modeling, our framework enables scalable simulation and rapid prototyping of next-generation quantum and spintronic devices. △ Less

Submitted 22 February, 2026; v1 submitted 25 October, 2025; originally announced October 2025.

Efficient bidirectional quantum frequency conversion between telecom and visible bands using programmable III-V nanophotonic waveguides

Authors: Jierui Hu, Hao Yuan, Joshua Akin, A. K. M. Naziul Haque, Yunlei Zhao, Kejie Fang

Abstract: Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional Q… ▽ More Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional QFC between the telecom (1550-nm) and visible (780-nm) bands using unpoled indium gallium phosphide (InGaP) $χ^{(2)}$ nanophotonic waveguides, eliminating the need for a long-wavelength pump. Leveraging the large nonlinear susceptibility of InGaP together with programmable modal-phase-matching control, we obtain record-low pump power (20 mW) -- an order of magnitude lower than that in previous demonstrations using integrated thin-film waveguides -- and record-high loss-inclusive normalized conversion efficiency among non-resonant QFC implementations. The platform maintains quantum coherence and entanglement of input photons with noise well below the single-photon level. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks. △ Less

Submitted 18 November, 2025; v1 submitted 18 October, 2025; originally announced October 2025.

Quantum Random Feature Method for Solving Partial Differential Equations

Authors: Junpeng Hu, Shi Jin, Nana Liu, Lei Zhang

Abstract: Quantum computing holds significant promise for scientific computing due to its potential for polynomial to even exponential speedups over classical methods, which are often hindered by the curse of dimensionality. While neural networks present a mesh-free alternative to solve partial differential equations (PDEs), their accuracy is difficult to achieve since one needs to solve a high-dimensional… ▽ More Quantum computing holds significant promise for scientific computing due to its potential for polynomial to even exponential speedups over classical methods, which are often hindered by the curse of dimensionality. While neural networks present a mesh-free alternative to solve partial differential equations (PDEs), their accuracy is difficult to achieve since one needs to solve a high-dimensional non-convex optimization problem using the stochastic gradient descent method and its variants, the convergence of which is difficult to prove and cannot be guaranteed. The classical random feature method (RFM) effectively merges advantages from both classical numerical analysis and neural network based techniques, achieving spectral accuracy and a natural adaptability to complex geometries. In this work, we introduce a quantum random feature method (QRFM) that leverages quantum computing to accelerate the classical RFM framework. Our method constructs PDE solutions using quantum-generated random features and enforces the governing equations via a collocation approach. A complexity analysis demonstrates that this hybrid quantum-classical algorithm can achieve a quadratic speedup over the classical RFM. △ Less

Submitted 9 October, 2025; originally announced October 2025.

Arbitrary Instantaneous Bandwidth Microwave Receiver via Scalable Rydberg Vapor Cell Array with Stark Comb

Authors: Yuechun Jiao, Yuwen Yin, Yunhui He, Jinlian Hu, Cheng Lu, Jingxu Bai, Zhengyang Bai, Weibin Li, Suotang Jia, Jianming Zhao

Abstract: Rydberg atoms have great potential for microwave (MW) measurements due to their high sensitivity, broad carrier bandwidth, and traceability. However, the narrow instantaneous bandwidth of the MW receiver limits its applications. Improving the instantaneous bandwidth of the receiver is an ongoing challenge. Here, we report on the achievement of an arbitrary instantaneous bandwidth MW receiver via a… ▽ More Rydberg atoms have great potential for microwave (MW) measurements due to their high sensitivity, broad carrier bandwidth, and traceability. However, the narrow instantaneous bandwidth of the MW receiver limits its applications. Improving the instantaneous bandwidth of the receiver is an ongoing challenge. Here, we report on the achievement of an arbitrary instantaneous bandwidth MW receiver via a linear array of scalable Rydberg vapor cells with Stark comb, where the Stark comb consists of an MW frequency comb (MFC) and a position-dependent Stark field. In the presence of the Stark field, the resonance MW transition frequency between two Rydberg states is position dependent, so that we can make each MFC line act as a local oscillator (LO) field to resonantly couple one Rydberg cell. Thus, each cell receives part of a broadband MW signal within its instantaneous bandwidth using atomic heterodyne detection, achieving the measurements of the broadband MW signal simultaneously. In our proof-of-principle experiment, we demonstrate the MW receiver with 210~MHz instantaneous bandwidth using an MFC field with 21 lines. Meanwhile, we achieve an overall sensitivity of 326.6~nVcm$^{-1}$Hz$^{-1/2}$. In principle, the method allows for achieving an arbitrary instantaneous bandwidth of the receiver, provided we have enough MFC lines with enough power. Our work paves the way to design and develop a scalable MW receiver for applications in radar, communication, and spectrum monitoring. △ Less

Submitted 30 September, 2025; originally announced September 2025.

Comments: 8 pages, 4 figures

Spontaneous excitation of a centripetally accelerated atom coupled to electromagnetic vacuum fluctuations near a reflecting boundary

Authors: Yan Peng, Jiawei Hu, Hongwei Yu

Abstract: We investigate the rate of change of the mean atomic energy for centripetally accelerated atoms interacting with electromagnetic vacuum fluctuations near a reflecting boundary, using the Dalibard-Dupont-Roc-Cohen-Tannoudji formalism. The distinct contributions from vacuum fluctuations and radiation reaction are analyzed separately. Our results reveal that, when the centripetal acceleration signifi… ▽ More We investigate the rate of change of the mean atomic energy for centripetally accelerated atoms interacting with electromagnetic vacuum fluctuations near a reflecting boundary, using the Dalibard-Dupont-Roc-Cohen-Tannoudji formalism. The distinct contributions from vacuum fluctuations and radiation reaction are analyzed separately. Our results reveal that, when the centripetal acceleration significantly exceeds the characteristic acceleration set by the atomic transition frequency, vacuum fluctuations dominates over radiation reaction, irrespective of the atom-boundary distance and the atomic polarization. In the near-zone regime, where the atom-boundary distance is much smaller than both the characteristic length associated with the acceleration and the transition wavelength of the atom, the boundary introduces substantial corrections to the rate of change of the mean atomic energy. These corrections are comparable in magnitude to those in free space and exhibit strong dependence on the atomic polarization. Remarkably, in the intermediate and far regions, contributions stemming from the combined effects of the boundary and acceleration can become the leading and subleading terms, respectively. An acceleration-independent term also arises from their interplay. These findings highlight the significant interplay between acceleration and the presence of a boundary in shaping atomic radiative properties and may have potential implications for experimentally probing the circular Unruh effect. △ Less

Submitted 19 September, 2025; originally announced September 2025.

Comments: 17 pages, 1 figure, published version

Journal ref: Phys. Rev. D 112, 065014 (2025)

Measurement-Driven Transitions between Area Law Phases

Authors: Hui Yu, Jiangping Hu

Abstract: In recent years, quantum circuits consisting of unitary gates and projective measurements have become valuable tools for stimulating or preparing quantum many-body states with non-trivial properties. Here, we introduce and examine a measurement-only circuit (the projective quantum Ising model with three-spin interactions) that involves three non-commuting projective measurements. This model featur… ▽ More In recent years, quantum circuits consisting of unitary gates and projective measurements have become valuable tools for stimulating or preparing quantum many-body states with non-trivial properties. Here, we introduce and examine a measurement-only circuit (the projective quantum Ising model with three-spin interactions) that involves three non-commuting projective measurements. This model features three distinct phases, separated by two critical lines. We utilize two entanglement measures (topological entanglement entropy and mutual information) to identify the phase boundaries and derive various critical exponents through scaling analysis. We establish a relationship between our model and a two-dimensional statistical model (bond percolation) within certain limits. We hope that our results will shed light on further studies using other measurement-only models. △ Less

Submitted 19 September, 2025; originally announced September 2025.

Comments: 8 pages, 11 figures

Journal ref: Phys. Scr. 100 065950 (2025)

Quantum Pontus-Mpemba Effects in Real and Imaginary-time Dynamics

Authors: Hui Yu, Jiangping Hu, Shi-Xin Zhang

Abstract: The quantum Pontus-Mpemba effect (QPME) is a counterintuitive phenomenon wherein a quantum system relaxes more rapidly through a two-step evolution protocol than through direct evolution under a symmetric Hamiltonian alone. In this protocol, the system first evolves under a symmetry-breaking Hamiltonian and then switches to a symmetric one. We demonstrate that QPME occurs under both real-time and… ▽ More The quantum Pontus-Mpemba effect (QPME) is a counterintuitive phenomenon wherein a quantum system relaxes more rapidly through a two-step evolution protocol than through direct evolution under a symmetric Hamiltonian alone. In this protocol, the system first evolves under a symmetry-breaking Hamiltonian and then switches to a symmetric one. We demonstrate that QPME occurs under both real-time and imaginary-time dynamics with respect to $U(1)$-symmetry. Using tilted ferromagnetic initial states, we demonstrate that a transient asymmetric evolution significantly accelerates thermalization or convergence to the ground state for both real-time and imaginary-time evolutions, respectively. The effect is pronounced for small tilt angles, while larger tilts or antiferromagnetic initial states suppress it. Numerical evidence across different system sizes confirms the robustness of QPME, demonstrating its stability in the thermodynamic limit. This work extends the framework of nonequilibrium quantum phenomena to incorporate active state preparation, with direct implications for the implementation of quantum simulation. △ Less

Submitted 9 April, 2026; v1 submitted 2 September, 2025; originally announced September 2025.

Comments: 11 pages, 6 figures with supplemental materials

Journal ref: Phys. Rev. B 113, 134304, 2026

Extended parameter shift rules with minimal derivative variance for parameterized quantum circuits

Authors: Zhijian Lai, Jiang Hu, Dong An, Zaiwen Wen

Abstract: Parameter shift rules (PSRs) are useful methods for computing arbitrary-order derivatives of the cost function in parameterized quantum circuits. The basic idea of PSRs is to evaluate the cost function at different parameter shifts, then use specific coefficients to combine them linearly to obtain the exact derivatives. In this work, we propose an extended parameter shift rule (EPSR) which general… ▽ More Parameter shift rules (PSRs) are useful methods for computing arbitrary-order derivatives of the cost function in parameterized quantum circuits. The basic idea of PSRs is to evaluate the cost function at different parameter shifts, then use specific coefficients to combine them linearly to obtain the exact derivatives. In this work, we propose an extended parameter shift rule (EPSR) which generalizes a broad range of existing PSRs and has the following two advantages. First, EPSR offers an infinite number of possible parameter shifts, allowing the selection of the optimal parameter shifts to minimize the final derivative variance and thereby obtaining the more accurate derivative estimates with limited quantum resources. Second, EPSR extends the scope of the PSRs in the sense that EPSR can handle arbitrary Hermitian operator $H$ in gate $U(x) = \exp (iHx)$ in the parameterized quantum circuits, while existing PSRs are valid only for simple Hermitian generators $H$ such as simple Pauli words. Additionally, we show that the widely used ``general PSR'', introduced by Wierichs et al. (2022), is a special case of our EPSR, and we prove that it yields globally optimal shifts for minimizing the derivative variance under the weighted-shot scheme. Finally, through numerical simulations, we demonstrate the effectiveness of EPSR and show that the usage of the optimal parameter shifts indeed leads to more accurate derivative estimates. △ Less

Submitted 7 December, 2025; v1 submitted 12 August, 2025; originally announced August 2025.

Comments: 33 pages, 6 figures

Journal ref: Physical Review Applied 25, no. 1 (2026): 014005

MiqroForge: An Intelligent Workflow Platform for Quantum-Enhanced Computational Chemistry

Authors: Jianan Wang, Wenbo Guo, Xin Yue, Minjie Xu, Yueqiang Zheng, Jingxiang Dong, Jiarui Hu, Jian Xia, Chuixiong Wu

Abstract: The connect-fill-run workflow paradigm, widely adopted in mature software engineering, accelerates collaborative development. However, computational chemistry, computational materials science, and computational biology face persistent demands for multi-scale simulations constrained by simplistic platform designs. We present MiqroForge, an intelligent cross-scale platform integrating quantum comput… ▽ More The connect-fill-run workflow paradigm, widely adopted in mature software engineering, accelerates collaborative development. However, computational chemistry, computational materials science, and computational biology face persistent demands for multi-scale simulations constrained by simplistic platform designs. We present MiqroForge, an intelligent cross-scale platform integrating quantum computing capabilities. By combining AI-driven dynamic resource scheduling with an intuitive visual interface, MiqroForge significantly lowers entry barriers while optimizing computational efficiency. The platform fosters a collaborative ecosystem through shared node libraries and data repositories, thereby bridging practitioners across classical and quantum computational domains. △ Less

Submitted 10 August, 2025; originally announced August 2025.

Hilbert subspace imprint: a new mechanism for non-thermalization

Authors: Hui Yu, Jiangping Hu, Shi-Xin Zhang

Abstract: The search for non-ergodic mechanisms in quantum many-body systems has become a frontier area of research in non-equilibrium physics. In this Letter, we introduce Hilbert subspace imprint (HSI)-a novel mechanism that enables evasion of thermalization and bridges the gap between quantum many-body scars (QMBS) and Hilbert space fragmentation (HSF). HSI manifests when initial states overlap exclusive… ▽ More The search for non-ergodic mechanisms in quantum many-body systems has become a frontier area of research in non-equilibrium physics. In this Letter, we introduce Hilbert subspace imprint (HSI)-a novel mechanism that enables evasion of thermalization and bridges the gap between quantum many-body scars (QMBS) and Hilbert space fragmentation (HSF). HSI manifests when initial states overlap exclusively with a polynomial scaling (with system size) set of eigenstates. We demonstrate this phenomenon through two distinct approaches: weak symmetry breaking and initial state engineering. In the former case, we observe that ferromagnetic states including those with a single spin-flip display non-thermal behavior under weak U(1) breaking, while antiferromagnetic states thermalize. In contrast, the Z2-symmetric model shows thermalization for both ferromagnetic and antiferromagnetic states. In the latter case, we engineer the initial state prepared by shallow quantum circuits that enhance the overlap with the small target subspace. Our results establish HSI as a mechanism equally fundamental to non-thermalization as QMBS and HSF. △ Less

Submitted 13 June, 2025; originally announced June 2025.

Comments: 5 pages, 5 figures with supplemental materials

Circuit-level-configurable Zero-field Superconducting Diodes: A Universal Platform Beyond Intrinsic Symmetry Breaking

Authors: Xiaofan Shi, Ziwei Dou, Dong Pan, Guoan Li, Yupeng Li, Anqi Wang, Zhiyuan Zhang, Xingchen Guo, Xiao Deng, Bingbing Tong, Zhaozheng Lyu, Peiling Li, Fanming Qu, Guangtong Liu, Jianhua Zhao, Jiangping Hu, Li Lu, Jie Shen

Abstract: Modern industry seeks next-generation microelectronics with ultra-low dissipation and noise beyond semiconducting systems, where the superconducting electronics offer promise. Its physical foundation is the superconducting diode effect (SDE) with nonreciprocal supercurrent. SDE has hitherto mainly relied on material-specific intrinsic symmetry breaking in superconductors, suffering from low yield,… ▽ More Modern industry seeks next-generation microelectronics with ultra-low dissipation and noise beyond semiconducting systems, where the superconducting electronics offer promise. Its physical foundation is the superconducting diode effect (SDE) with nonreciprocal supercurrent. SDE has hitherto mainly relied on material-specific intrinsic symmetry breaking in superconductors, suffering from low yield, controllability, and compatibility with further functional extension - an undesirable aspect for applications. Here, we demonstrated a field-free SDE due to the chemical potential shift from external circuit line resistance, which is generic and challenges the previous interpretations of the intrinsic symmetry breaking in superconductivity for zero-field SDE. Moreover, this SDE is circuit-level configurable since it can be electrically switched on/off with its polarity and efficiency precisely modulated via gate voltage and circuit reconfiguration, facilitating functional extension. Such a generic, controllable and extensible SDE addresses critical challenges in dissipationless circuit towards application, and thus establishes a robust platform for scalable superconducting electronics. △ Less

Submitted 23 May, 2025; originally announced May 2025.

Observation of Near-Critical Kibble-Zurek Scaling in Rydberg Atom Arrays

Authors: Tao Zhang, Hanteng Wang, Wenjun Zhang, Yuqing Wang, Angrui Du, Ziqi Li, Yujia Wu, Chengshu Li, Jiazhong Hu, Hui Zhai, Wenlan Chen

Abstract: The Kibble-Zurek scaling reveals the universal dynamics when a system is linearly ramped across a symmetry-breaking phase transition. However, in reality, inevitable finite-size effects or symmetrybreaking perturbations can often smear out the critical point and render the phase transition into a smooth crossover. In this letter, we show experimentally that the precise Kibble-Zurek scaling can be… ▽ More The Kibble-Zurek scaling reveals the universal dynamics when a system is linearly ramped across a symmetry-breaking phase transition. However, in reality, inevitable finite-size effects or symmetrybreaking perturbations can often smear out the critical point and render the phase transition into a smooth crossover. In this letter, we show experimentally that the precise Kibble-Zurek scaling can be retained in the near-critical crossover regime, not necessarily crossing the critical point strictly. The key ingredient to achieving this near-critical Kibble-Zurek scaling is that the system size and the symmetry-breaking field must be appropriately scaled following the variation of ramping speeds. The experiment is performed in a reconfigurable Rydberg atom array platform, where the Rydberg blockade effect induces a Z2 symmetry-breaking transition. The atom array platform enables precise control of the system size and the zigzag geometry as a symmetry-breaking field. Therefore, we can demonstrate notable differences in the precision of the Kibble-Zurek scaling with or without properly scaling the system size and the zigzag geometry. Our results strengthen the Kibble-Zurek scaling as an increasingly valuable tool for investigating phase transition in quantum simulation platforms. △ Less

Submitted 12 May, 2025; originally announced May 2025.

Comments: 16 pages, 11 figures

Journal ref: Phys. Rev. Lett. 135, 093403 (2025)

Observation of modulation-induced Feshbach resonance

Authors: Tongkang Wang, Yuqi Liu, Jundong Wang, Youjia Huang, Wenlan Chen, Zhendong Zhang, Jiazhong Hu

Abstract: In this work, we observe a novel resonant mechanism, namely the modulation-induced Feshbach resonance. By applying a far-detuned laser to the cesium D2 transition with intensity modulation, we periodically shake the energy levels of atomic collisional states. This periodic shaking connects the free-scattering states to shallow molecular states. At specific frequencies, we observe significant atom… ▽ More In this work, we observe a novel resonant mechanism, namely the modulation-induced Feshbach resonance. By applying a far-detuned laser to the cesium D2 transition with intensity modulation, we periodically shake the energy levels of atomic collisional states. This periodic shaking connects the free-scattering states to shallow molecular states. At specific frequencies, we observe significant atom loss, which corresponds to the resonant coupling between these two types of states. This precisely corresponds to a form of Feshbach resonance, yet in the frequency domain rather than the magnetic-field domain. Using this method, we can directly scan the energy spectrum of molecular bound states without synthesizing any molecules. In addition to these bound states, we can also probe the molecular states embedded in the continuum, which are typically very difficult to detect by the conventional methods based on molecular synthesis. Moreover, by using a far-detuned laser instead of a magnetic field coil, it enables spatially dependent control over atomic interactions, coupling multiple levels simultaneously, and inducing new Feshbach resonances for those atoms that do not have conventional magnetic resonances. Therefore, we believe that this new resonant mechanism offers new opportunities for controlling atomic and molecular interactions in quantum simulations. △ Less

Submitted 19 October, 2025; v1 submitted 11 May, 2025; originally announced May 2025.

Comments: 7 pages, 4 figures

Journal ref: Phys. Rev. Lett. 135, 203201 (2025)

Nonlocal Coherent Optical Nonlinearities of a Macroscopic Quantum System

Authors: Albert Liu, Eric W. Martin, Jiaqi Hu, Zhaorong Wang, Hui Deng, Steven T. Cundiff

Abstract: The optical responses of solids are typically understood to be local in space. Whether locality holds for the optical response of a macroscopic quantum system has, however, been largely unexplored. Here, we use multidimensional coherent spectroscopy at the optical diffraction limit to demonstrate nonlocal optical nonlinearities in a semiconductor microcavity. These nonlocal optical responses are b… ▽ More The optical responses of solids are typically understood to be local in space. Whether locality holds for the optical response of a macroscopic quantum system has, however, been largely unexplored. Here, we use multidimensional coherent spectroscopy at the optical diffraction limit to demonstrate nonlocal optical nonlinearities in a semiconductor microcavity. These nonlocal optical responses are both coherent and quantum in nature, deriving from the macroscopic length scale of confined exciton-polariton wavefunctions. △ Less

Submitted 18 April, 2025; originally announced April 2025.

Fast microwave-driven two-qubit gates between fluxonium qubits with a transmon coupler

Authors: Siddharth Singh, Eugene Y. Huang, Jinlun Hu, Figen Yilmaz, Martijn F. S. Zwanenburg, Piranavan Kumaravadivel, Siyu Wang, Taryn V. Stefanski, Christian Kraglund Andersen

Abstract: Two qubit gates constitute fundamental building blocks in the realization of large-scale quantum devices. Using superconducting circuits, two-qubit gates have previously been implemented in different ways with each method aiming to maximize gate fidelity. Another important goal of a new gate scheme is to minimize the complexity of gate calibration. In this work, we demonstrate a high-fidelity two-… ▽ More Two qubit gates constitute fundamental building blocks in the realization of large-scale quantum devices. Using superconducting circuits, two-qubit gates have previously been implemented in different ways with each method aiming to maximize gate fidelity. Another important goal of a new gate scheme is to minimize the complexity of gate calibration. In this work, we demonstrate a high-fidelity two-qubit gate between two fluxonium qubits enabled by an intermediate capacitively coupled transmon. The coupling strengths between the qubits and the coupler are designed to minimize residual crosstalk while still allowing for fast gate operations. The gate is based on frequency selectively exciting the coupler using a microwave drive to complete a 2$π$ rotation, conditional on the state of the fluxonium qubits. When successful, this drive scheme implements a conditional phase gate. Using analytically derived pulse shapes, we minimize unwanted excitations of the coupler and obtain gate errors of $10^{-2}$ for gate times below 60~ns. At longer durations, our gate is limited by relaxation of the coupler. Our results show how carefully designed control pulses can speed up frequency selective entangling gates. △ Less

Submitted 22 April, 2025; v1 submitted 18 April, 2025; originally announced April 2025.

Impact of helium ion irradiation on the thermal properties of superconducting nanowire single-photon detectors

Authors: Yi-Yu Hong, Yu-Ze Wang, Wei-Jun Zhang, Jia-Hao Hu, Jia-Min Xiong, Dong-Wei Chu, Xin Ou, Wen-Tao Wu, Xiao-Fu Zhang, Hui-Qin Yu, Pu-Sheng Yuan, Hao Li, Ling Wu, Zhen Wang, Li-Xing You

Abstract: SNSPDs are indispensable for applications ranging from quantum information processing to deep-space optical communications, owing to their high detection efficiency, low dark counts, and excellent timing resolution. However, further improving the intrinsic detection efficiency (IDE) remains crucial for optimizing SNSPD performance. Ion irradiation has recently emerged as a powerful post-fabricatio… ▽ More SNSPDs are indispensable for applications ranging from quantum information processing to deep-space optical communications, owing to their high detection efficiency, low dark counts, and excellent timing resolution. However, further improving the intrinsic detection efficiency (IDE) remains crucial for optimizing SNSPD performance. Ion irradiation has recently emerged as a powerful post-fabrication method to enhance SNSPD characteristics. Here, we studied the effects of He-ion irradiation on the thermal properties of NbN SNSPDs. We systematically examine the evolution of thermal boundary conductance as a function of ion fluence (0-1.1E17 ions/cm2), observing a 57% decrease from 127 to 54 W/m^2K^4 with increasing fluence, followed by saturation at approximately 9E16 ions/cm2. At this fluence, the minimum hotspot relaxation time measurements indicate a 41% increase, rising from 17 to 24 ps,while the electron-phonon interaction time decreases, with the magnitude of change depending on temperature and sample batch.TEM reveals defect formation at the NbN/SiO2 interface (6-8 nm) and He-bubble formation within the SiO2 layer (30-260 nm), contributing to the extended thermal relaxation time. These irradiation-induced modifications play a key role in enhancing the IDE of the treated devices. We further demonstrate a post-irradiation SNSPD showing a saturated IDE plateau at 2000 nm from 2.7 K to 28 mK, enabled by thermal modifications and a weakly wavelength-dependent avalanche-assisted mechanism. Our findings highlight ion irradiation as a valuable tool for thermal tailoring in SNSPDs and advance the understanding of detection physics and defect engineering in superconducting optoelectronics. △ Less

Submitted 13 November, 2025; v1 submitted 3 April, 2025; originally announced April 2025.

Comments: 18 pages, 6 figures, 1 table

Journal ref: Superconductor Science and Technology 38(11), 115013 (2025)

A quantum gradient descent algorithm for optimizing Gaussian Process models

Authors: Junpeng Hu, Jinglai Li, Lei Zhang, Shi Jin

Abstract: Gaussian Process Regression (GPR) is a nonparametric supervised learning method, widely valued for its ability to quantify uncertainty. Despite its advantages and broad applications, classical GPR implementations face significant scalability challenges, as they involve matrix operations with a cubic complexity in relation to the dataset size. This computational challenge is further compounded by t… ▽ More Gaussian Process Regression (GPR) is a nonparametric supervised learning method, widely valued for its ability to quantify uncertainty. Despite its advantages and broad applications, classical GPR implementations face significant scalability challenges, as they involve matrix operations with a cubic complexity in relation to the dataset size. This computational challenge is further compounded by the demand of optimizing the Gaussian Process model over its hyperparameters, rendering the total computational cost prohibitive for data intensive problems. To address this issue, we propose a quantum gradient descent algorithm to optimize the Gaussian Process model. Taking advantage of recent advances in quantum algorithms for linear algebra, our algorithm achieves exponential speedup in computing the gradients of the log marginal likelihood. The entire gradient descent process is integrated into the quantum circuit. Through runtime analysis and error bounds, we demonstrate that our approach significantly improves the scalability of GPR model optimization, making it computationally feasible for large-scale applications. △ Less

Submitted 22 March, 2025; originally announced March 2025.