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中国科学:物理学 力学 天文学（英文版）
中国科学:物理学 力学 天文学（英文版）

周光召

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中国科学:物理学 力学 天文学（英文版）/Journal Science China(Physics, Mechanics&Astronomy)CSCDCSTPCDEISCI
查看更多>>《中国科学》是中国科学院主办、中国科学杂志社出版的自然科学专业性学术刊物。《中国科学》任务是反映中国自然科学各学科中的最新科研成果，以促进国内外的学术交流。《中国科学》以论文形式报道中国基础研究和应用研究方面具有创造性的、高水平的和有重要意义的科研成果。在国际学术界，《中国科学》作为代表中国最高水平的学术刊物也受到高度重视。国际上最具有权威的检索刊物SCI，多年来一直收录《中国科学》的论文。1999年《中国科学》夺得国家期刊奖的第一名。
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    Determination of molecular energies via variational-based quantum imaginary time evolution in a superconducting qubit system

    Zhiwen ZongSainan HuaiTianqi CaiWenyan Jin...
    1-11页
    查看更多>>摘要：As a valid tool for solving ground state problems,imaginary time evolution(ITE)is widely used in physical and chemical sim-ulations.Different ITE-based algorithms in their quantum counterpart have recently been proposed and applied to some real systems.We experimentally realize the variational-based quantum imaginary time evolution(QITE)algorithm to simulate the ground state energy of hydrogen(H2)and lithium hydride(LiH)molecules in a superconducting qubit system.The H2 molecule is directly simulated using the 3-qubit circuit with unitary-coupled clusters(UCC)ansatz.We also combine QITE with the cluster mean-field(CMF)method to obtain an effective Hamiltonian.The LiH molecule is correspondingly simulated using the 3-qubit circuit with hardware-efficient ansatz.For comparison,the LiH molecule is also directly simulated using the 4-qubit circuit with UCC ansatz at the equilibrium point.All the experimental results show a convergence within 4 iterations,with high-fidelity ground state energy obtained.For a more complex system in the future,the CMF may allow further grouping of interactions to obtain an effective Hamiltonian,then the hybrid QITE algorithm can possibly simulate a relatively large-scale system with fewer qubits.
      原文链接:
    • 万方数据
    • 维普

    A cost-efficient quantum access network with qubit-based synchronization

    Chunfeng HuangYe ChenTingting LuoWenjie He...
    12-22页
    查看更多>>摘要：Quantum key distribution(QKD)is a physical layer encryption technique that enables two distant parties to exchange secure keys with information-theoretic security.In the last two decades,QKD has transitioned from laboratory research to real-world ap-plications,including multi-user quantum access networks(QANs).This network structure allows users to share a single-photon detector at a network node through time-division multiplexing,thereby significantly reducing the network cost.However,cur-rent QAN implementations require additional hardware for auxiliary tasks such as time synchronization.To address this issue,we propose a cost-efficient QAN that uses qubit-based synchronization.In this approach,the transmitted qubits facilitate time synchronization,eliminating the need for additional synchronization hardware.We tested our scheme by implementing a net-work for two users and successfully achieved average secure key rates of 53.84 kbps and 71.90 kbps for each user over a 50-km commercial fiber spool.In addition,we investigated the capacity of the access network under cross-talk and loss conditions.The simulation results demonstrate that this scheme can support a QAN with 64 users with key rates up to 1070 bps.Our work provides a feasible and cost-effective way to implement a multi-user QKD network,further promoting the widespread application of QKD.
      原文链接:
    • 万方数据
    • 维普

    Nonreciprocal generation of Schr?dinger cat state induced by topology

    Zi-Hao LiLi-Li ZhengYing WuXin-You Lü...
    23-30页
    查看更多>>摘要：The Schrödinger cat state produced differently in two directions is anticipated to be a critical quantum resource in quantum infor-mation technologies.By exploring the interplay between quantum nonreciprocity and topology in a one-dimensional microcavity array,we obtain the Schrödinger cat state(a pure quantum state)in a chosen direction at the edge cavity,whereas a classical state in the other direction.This nonreciprocal generation of the cat state originates from the topologically protected chirality-mode excitation in the nontrivial phase,but in the trivial phase,the nonreciprocal generation of cat state vanishes.Thus,our proposal is switchable by tuning the parameters so that a topological phase transition occurs.Moreover,the obtained cat state has nonreciprocal high fidelity,nonclassicality,and quantum coherence,which are sufficient to be used in various one-way quantum technologies,e.g.,invisible quantum sensing,noise-tolerant quantum computing,and chiral quantum networks.Our work pro-vides a general approach to control quantum nonreciprocities with the topological effect,which substantially broadens the fields of nonreciprocal photonics and topological physics.
      原文链接:
    • 万方数据

    Gravitational waves and primordial black hole productions from gluodynamics by holography

    Song HeLi LiZhibin LiShao-Jiang Wang...
    31-42页
    查看更多>>摘要：Understanding the nature of quantum chromodynamics(QCD)matter is important but challenging due to the presence of non-perturbative dynamics under extreme conditions.We construct a holographic model describing the gluon sector of QCD at finite temperatures in the non-perturbative regime.The equation of state as a function of temperature is in good accordance with the lattice QCD data.Moreover,the Polyakov loop and the gluon condensation,which are proper order parameters to capture the deconfinement phase transition,also agree quantitatively well with the lattice QCD data.We obtain a strong first-order con-finement/deconfinement phase transition at Tc=276.5 MeV that is consistent with the lattice QCD prediction.Based on our model for a pure gluon hidden sector,we compute the stochastic gravitational waves and primordial black hole(PBH)produc-tions from this confinement/deconfinement phase transition in the early Universe.The resulting stochastic gravitational-wave backgrounds are found to be within detectability in the International Pulsar Timing Array and Square Kilometre Array in the near future when the associated productions of PBHs saturate the current observational bounds on the PBH abundances from the LIGO-Virgo-Collaboration O3 data.
      原文链接:
    • 万方数据
    • 维普

    Cosmological interpretation for the stochastic signal in pulsar timing arrays

    Yu-Mei WuZu-Cheng ChenQing-Guo Huang
    43-50页
    查看更多>>摘要：The pulsar timing array(PTA)collaborations have recently reported compelling evidence for a stochastic signal consistent with a gravitational-wave background.In this paper,we combine the latest data sets from NANOGrav,PPTA,and EPTA to explore cosmological interpretations for the PTA signal from first-order phase transitions,domain walls,and cosmic strings,respectively.We find that the domain wall model is strongly disfavored with the Bayes factors compared with the first-order phase transitions and cosmic strings being 1/90 and 1/189,respectively,breaking the degeneracy among these models in individual data set.We also find that:(1)a strong phase transition at temperatures below the electroweak scale is favored,and the bubble collisions make the dominant contribution to the energy density spectrum;(2)a small reconnection probability p＜1.55 × 10-1 allowed by strings in(super)string theory is favored at the 95％confidence level,and ground-based detectors can further constrain the parameter space.
      原文链接:
    • 万方数据
    • 维普

    Uncovering hidden nodes and hidden links in complex dynamic networks

    Zhaoyang ZhangXinyu WangHaihong LiYang Chen...
    51-63页
    查看更多>>摘要：Inferring network structures from available data has attracted much interest in network science;however,in many realistic net-works,only some of the nodes are perceptible while others are hidden,making it a challenging task.In this work,we develop a method for reconstructing the network with hidden nodes and links,taking account of fast-varying noise and time-delay inter-actions.By calculating the correlations of available data with different derivative orders for multiple pairs of accessible nodes,analyzing and integrating the relationships between different correlations,and defining diverse hidden-node-related reconstruction motifs,we can effectively identify the hidden nodes and hidden links in the network.
      原文链接:
    • 万方数据
    • 维普

    Color-kinematics duality and dual conformal symmetry for a four-loop form factor in N=4 SYM

    Guanda LinGang YangSiyuan Zhang
    64-71页
    查看更多>>摘要：We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only manifests all dual Jacobi relations via CK duality but also contains 133 free parameters.This suggests the constructibility of the form factor at even higher loops via CK duality.We also find that the planar form factor has a hidden dual conformal symmetry in the lightlike limit of the operator momentum,which is checked up to four loops.
      原文链接:
    • 万方数据
    • 维普

    Single-shot phase retrieval for randomly fluctuated and obstructed vortex beams

    Hao ZhangJun'an ZhuXingyuan LuZhiquan Hu...
    72-80页
    查看更多>>摘要：Vortex beams with orbital angular momentum play a crucial role in increasing the information capacity in optical commu-nications.The magnitude of orbital angular momentum determines the ability of information encoding.In practice,a vortex beam can encounter random objects or turbulence during free-space propagation,resulting in information damage.Therefore,accurately measuring the orbital angular momentum of a randomly fluctuated and obstructed vortex beam is a considerable challenge.Herein,we propose a single-shot method for the phase retrieval of a randomly fluctuated and obstructed vortex beam by combining the phase-shift theorem and self-reference holography.Experimental results reveal that the sign and magnitude of the initial orbital angular momentum can be simultaneously determined based on their quantitative relation with the number of coherence singularities on the observation plane,thus addressing the effects of random occlusion and atmospheric turbulence.The proposed method considerably improved the accurate decoding of orbital angular momentum information in nonideal free-space optical communications.
      原文链接:
    • 万方数据
    • 维普

    Enhanced wide-angle third-harmonic generation in flat-band-engineered quasi-BIC metagratings

    Yijia ZangRuoheng ChaiWenwei LiuZhancheng Li...
    81-87页
    查看更多>>摘要：Nonlinear metasurfaces and photonic crystals provide a significant way to generate and manipulate nonlinear signals owing to the resonance-and symmetry-based light-matter interactions supported by the artificial structures.However,the nonlinear conversion efficiency is generally limited by the angular dispersion of optical resonances especially in nonparaxial photonics.Here,we propose a metagrating realizing a quasi-bound-state in the continuum in a flat band to dramatically improve the third harmonic generation(THG)efficiency.A superior operating angular range is achieved based on the interlayer and intralayer couplings,which are introduced by breaking the mirror symmetry of the metagrating.We demonstrate the relation of angular dispersion between the nonlinear and linear responses at different incident angles.We also elucidate the mechanism of these off-axis flat-band-based nonlinear conversions through different mode decomposition.Our scheme provides a robust and analytical way for nonparaxial nonlinear generation and paves the way for further applications such as wide-angle nonlinear information transmission and enhanced nonlinear generation under tight focusing.
      原文链接:
    • 万方数据
    • 维普

    Robust boundary-induced bulk propagations in elastic waveguides with nonplanar surfaces

    Baizhan XiaJielong ZhangZihan JiangJianting Liu...
    88-96页
    查看更多>>摘要：Trivial elastic waveguides induced by line defects and nontrivial elastic waveguides protected by topological edge states have been extensively examined in planar waveguide systems.Despite these investigations,little is known about topologically protected bulk states and their resulting robust transmission properties,especially in nonplanar elastic waveguides with folded,curved,and twisted surfaces.Elastic Dirac waveguides with robust boundary-induced bulk states are presented.These states arise from the truncated boundaries of bulks with linear Dirac conical dispersions,differing from topologically protected edge states ensured by the bulk-edge correspondence.Experimental proof is provided,in which boundary-induced bulk states show robustly high-throughput transmissions along the waveguides,even with folded,curved,and twisted surfaces.These results not only open up new avenues for examining novel topological phenomena about bulk but also offer new platforms for developing topological devices with nonplanar surfaces.
      原文链接:
    • 万方数据
    • 维普