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arXiv 2022年

作者： Shao, Zhibin Li, Shaojian Liu, Yanzhao Li, Zi Wang, Huichao Bian, Qi Yan, Jiaqiang Mandrus, David Liu, Haiwen Zhang, Ping Xie, X.C. Wang, Jian Pan, Minghu School of Physics and Information Technology Shaanxi Normal University Xi’an710119 China School of Physics Huazhong University of Science and Technology Wuhan430074 China International Center for Quantum Materials School of Physics Peking University Beijing100871 China Institute of Applied Physics and Computational Mathematics Beijing100088 China School of Physics Sun Yat-sen University Guangzhou510275 China Materials Science and Technology Division Oak Ridge National Laboratory Oak RidgeTN37831 United States Department of Materials Science and Engineering University of Tennessee KnoxvilleTN37996 United States Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing100875 China School of Physics and Physical Engineering Qufu Normal University Qufu273165 China Collaborative Innovation Center of Quantum Matter Beijing100871 China Cas Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China Beijing Academy of Quantum Information Sciences Beijing100193 China

Recently, log-periodic quantum oscillations have been detected in topological materials zirconium pentatelluride (ZrTe5) and hafnium pentatelluride (HfTe5), displaying intriguing discrete scale invariance (DSI) characteristic. In condensed materials, the DSI is considered to be related to the quasi-bound states formed by massless Dirac fermions with strong Coulomb attraction, offering a feasible platform to study the long-pursued atomic-collapse phenomenon. Here, we demonstrate that a variety of atomic vacancies in the topological material HfTe5can host the geometric quasi-bound states with DSI feature, resembling the artificial supercritical atom collapse. The density of states of these quasi-bound states are enhanced and the quasi-bound states are spatially distributed in the "orbitals" surrounding the vacancy sites, which are detected and visualized by low-temperature scanning tunneling microscope/spectroscopy (STM/S). By applying the perpendicular magnetic fields, the quasi-bound states at lower energies become wider and eventually invisible, meanwhile the energies of quasi-bound states move gradually towards the Fermi energy (EF). These features are consistent with the theoretical prediction of a magnetic-field-induced transition from supercritical to subcritical states. The direct observation of geometric quasi-bound states sheds light on the deep understanding of the DSI in quantum materials. © 2022, CC BY.

关键词： Atoms

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Observation of Strong and Weak Thermalization in a Superconducting Quantum Processor

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Physical Review Letters 2021年第2期127卷 020602-020602页

作者： Fusheng Chen Zheng-Hang Sun Ming Gong Qingling Zhu Yu-Ran Zhang Yulin Wu Yangsen Ye Chen Zha Shaowei Li Shaojun Guo Haoran Qian He-Liang Huang Jiale Yu Hui Deng Hao Rong Jin Lin Yu Xu Lihua Sun Cheng Guo Na Li Futian Liang Cheng-Zhi Peng Heng Fan Xiaobo Zhu Jian-Wei Pan Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China Shanghai Branch CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 China Shanghai Research Center for Quantum Sciences Shanghai 201315 China Institute of Physics Chinese Academy of Sciences Beijing 100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing 100190 China Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama 351-0198 Japan Songshan Lake Materials Laboratory Dongguan 523808 Guangdong China CAS Center for Excellent in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

We experimentally study the ergodic dynamics of a 1D array of 12 superconducting qubits with a transverse field, and identify the regimes of strong and weak thermalization with different initial states. We observe convergence of the local observable to its thermal expectation value in the strong-thermalizaion regime. For weak thermalization, the dynamics of local observable exhibits an oscillation around the thermal value, which can only be attained by the time average. We also demonstrate that the entanglement entropy and concurrence can characterize the regimes of strong and weak thermalization. Our work provides an essential step toward a generic understanding of thermalization in quantum systems.

关键词： Eigenstate thermalization Quantum simulation Quantum statistical mechanics Spin dynamics 1-dimensional spin chains Superconducting qubits

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Coulomb Instabilities of a Three-Dimensional Higher-Order Topological Insulator

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Physical Review Letters 2021年第17期127卷 176601-176601页

作者： Peng-Lu Zhao Xiao-Bin Qiang Hai-Zhou Lu X. C. Xie Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology (SUSTech) Shenzhen 518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Shenzhen 518055 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Beijing Academy of Quantum Information Sciences West Building 3 No. 10 Xibeiwang East Road Haidian District Beijing 100193 China

Topological insulators (TIs) are an exciting discovery because of their robustness against disorder and interactions. Recently, second-order TIs have been attracting increasing attention, because they host topologically protected 1D hinge states in 3D or 0D corner states in 2D. A significantly critical issue is whether the second-order TIs also survive interactions, but it is still unexplored. We study the effects of weak Coulomb interactions on a 3D second-order TI, with the help of renormalization-group calculations. We find that the 3D second-order TIs are always unstable, suffering from two types of topological phase transitions. One is from second-order TI to TI, the other is to normal insulator. The first type is accompanied by emergent time-reversal and inversion symmetries and has a dynamical critical exponent κ=1. The second type does not have the emergent symmetries but has nonuniversal dynamical critical exponents κ<1. Our results may inspire more inspections on the stability of higher-order topological states of matter and related novel quantum criticalities.

关键词： Topological insulators Topological phase transition Renormalization group

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A two-stage solution to quantum process tomography: error analysis and optimal design

arXiv

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arXiv 2024年

作者： Xiao, Shuixin Wang, Yuanlong Zhang, Jun Dong, Daoyi Mooney, Gary J. Petersen, Ian R. Yonezawa, Hidehiro School of Engineering and Technology University of New South Wales CanberraACT2600 Australia University of Michigan–Shanghai Jiao Tong University Joint Institute Shanghai Jiao Tong University Shanghai200240 China School of Engineering The Australian National University CanberraACT2601 Australia Key Laboratory of Systems and Control Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing100190 China CIICADA Lab School of Engineering Australian National University ACT2601 Australia School of Physics The University of Melbourne ParkvilleVIC3010 Australia School of Physics University of Melbourne ParkvilleVIC3010 Australia School of Engineering Australian National University ACT2601 Australia RIKEN Center for Quantum Computing Japan Centre for Quantum Computation and Communication Technology Australian Research Council CanberraACT2600 Australia

Quantum process tomography is a critical task for characterizing the dynamics of quantum systems and achieving precise quantum control. In this paper, we propose a two-stage solution for both trace-preserving and non-trace-preserving quantum process tomography. Utilizing a tensor structure, our algorithm exhibits a computational complexity of O(MLd2) where d is the dimension of the quantum system and M, L represent the numbers of different input states and measurement operators, respectively. We establish an analytical error upper bound and then design the optimal input states and the optimal measurement operators, which are both based on minimizing the error upper bound and maximizing the robustness characterized by the condition number. Numerical examples and testing on IBM quantum devices are presented to demonstrate the performance and efficiency of our algorithm. Copyright © 2024, The Authors. All rights reserved.

关键词： Error analysis

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Absolute triple differential cross sections for low-energy electron impact ionization of biochemically relevant systems: Water, tetrahydrofuran, and hydrated tetrahydrofuran

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Physical Review A 2021年第1期104卷 012817-012817页

作者： Jiaqi Zhou Esam Ali Maomao Gong Shaokui Jia Yutian Li Yingying Wang Zhen Zhang Xiaorui Xue Dmitry V. Fursa Igor Bray Xiangjun Chen Don Madison Alexander Dorn Xueguang Ren School of Physics Xi'an Jiaotong University Xi'an 710049 China Max-Planck-Institut für Kernphysik Saupfercheckweg 1 69117 Heidelberg Germany Department of Natural Sciences D. L. Hubbard Center for Innovation Northwest Missouri State University Maryville Missouri 64468 USA Department of Physics Faculty of Arts & Sciences-El Marj University of Benghazi El Marj Libya Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Hefei Anhui 230026 China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 China Curtin Institute for Computation and Department of Physics and Astronomy Curtin University GPO Box U1987 Perth WA 6845 Australia Department of Physics Missouri University of Science and Technology Rolla Missouri 65409 USA

An experimental procedure is reported, which provides the absolute triple differential cross sections (ATDCSs) for electron-impact ionization of large (bio)molecules. This type of measurements represents the most stringent tests for new or existing theoretical models. We will use this procedure to test the accuracy of the best currently available theoretical models for the problems of electron-impact (65 eV) ionization of the molecules water (H2O), tetrahydrofuran (C4H8O), and their hydrogen-bonded dimer H2O·C4H8O. The cross sections were calculated using the molecular three-body distorted-wave (M3DW) model, the multicenter three-distorted-wave (MCTDW) approach, and the multicenter three-distorted-wave using the Ward-Macek approximation (MCTDW-WM). When compared to the new experimental ATDCS results which cover almost the full solid angle of the ejected electron and a broad range of ejected electron energies and projectile scattering angles, it is found that the data for water are generally well reproduced by the M3DW model, while strong deviations in the absolute magnitude of the cross sections are found for the MCTDW. The MCTDW-WM model provides improved agreement over the MCTDW. These theoretical models, however, become less adequate for the ATDCS of C4H8O, in particular concerning the absolute magnitude. Furthermore, we find that a water environment can play a noticeable role for the ionization dynamics in the case of hydrated molecules.

关键词： Electron & positron scattering Electronic excitation & ionization

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Characterization of a microsecond pulsed non-equilibrium atmospheric pressure Ar plasma using laser scattering and optical emission spectroscopy

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Plasma science and technology 2020年第6期22卷 120-127页

作者： Fengdong JIA Yong WU Qi MIN Maogen SU Keigo TAKEDA Kenji ISHIKAWA Hiroki KONDO Makoto SEKINE Masaru HORI Zhiping ZHONG School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049People's Republic of China Institute of Applied Physics and Computational Mathematics Beijing 100088People's Republic of China Key Laboratory of Atomic and Molecular Physics&Functional Material of Gansu Province College of Physics and Electronic EngineeringNorthwest Normal UniversityLanzhou 730070People's Republic of China Department of Electrical and Electronic Engineering Faculty of Science and TechnologyMeijo UniversityNagoya 468-8502Japan Graduate School of Engineering Nagoya UniversityNagoya 464-8603Japan CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190People's Republic of China

A non-equilibrium atmospheric pressure argon(Ar)plasma excited by microsecond pulse is studied experimentally by laser scattering and optical emission spectroscopy(OES),and theoretically by collisional-radiative(CR)*** specifically,the electron temperature and electron density of plasma are obtained directly by the laser Thomson scattering,the gas temperature is measured by laser Raman scattering,the optical emissions of excited Ar states of plasma are measured by *** laser scattering results show that the electron temperature is about 1 eV which is similar to that excited by 60 Hz AC power,but the gas temperature is as low as 300 K compared to about 700 K excited by 60 Hz AC *** is shown that the microsecond pulsed power supply,rather than nanosecond ones,is short enough to reduce the gas temperature of atmospheric pressure plasma to near room *** electron temperature and electron density are also obtained by CR model based on OES,and find that the intensities of the optical emission intensity lines of 727.41,811.73,841.08,842.83,852.44 and 912.86 nm of Ar can be used to characterize the behavior of electron density and electron temperature,it is very useful to quickly estimate the activity of the atmospheric pressure Ar plasma in many applications.

关键词： plasma diagnosis laser Thomson scattering atmospheric pressure plasma

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Quantum generative training using rényi divergences

arXiv

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arXiv 2021年

作者： Kieferová, Mária Marrero, Carlos Ortiz Wiebe, Nathan Centre for Quantum Computation and Communication Technology Centre for Quantum Software and Information University of Technology Sydney Data Sciences & Analytics Group Department of Electrical & Computer Engineering Pacific Northwest National Laboratory North Carolina State University Department of Computer Science Department of Physics High Performance Computing Group University of Toronto University of Washington Pacific Northwest National Laboratory

Quantum neural networks (QNNs) are a framework for creating quantum algorithms that promises to combine the speedups of quantum computation with the widespread successes of machine learning. A major challenge in QNN development is a concentration of measure phenomenon known as a barren plateau that leads to exponentially small gradients for a range of QNNs models. In this work, we examine the assumptions that give rise to barren plateaus and show that an unbounded loss function can circumvent the existing no-go results. We propose a training algorithm that minimizes the maximal Rényi divergence of order two and present techniques for gradient computation. We compute the closed form of the gradients for Unitary QNNs and Quantum Boltzmann Machines and provide sufficient conditions for the absence of barren plateaus in these models. We demonstrate our approach in two use cases: thermal state learning and Hamiltonian learning. In our numerical experiments, we observed rapid convergence of our training loss function and frequently archived a 99% average fidelity in fewer than 100 epochs. © 2021, CC BY.

关键词： Quantum computers

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Kilohertz quasiperiodic oscillations in short gamma-ray bursts

arXiv

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arXiv 2023年

作者： Chirenti, Cecilia Dichiara, Simone Lien, Amy Miller, M. Coleman Preece, Robert Department of Astronomy University of Maryland College ParkMD20742 United States Astroparticle Physics Laboratory NASA/GSFC GreenbeltMD20771 United States Center for Research and Exploration in Space Science and Technology NASA/GSFC GreenbeltMD20771 United States Center for Mathematics Computation and Cognition UFABC SP Santo Andre09210-170 Brazil Department of Astronomy and Astrophysics The Pennsylvania State University 525 Davey Lab University ParkPA16802 United States Department of Chemistry Biochemistry and Physics University of Tampa 401 W. Kennedy Blvd TampaFL33606 United States Department of Space Science University of Alabama in Huntsville HuntsvilleAL35899 United States

Short γ-ray bursts are associated with binary neutron star mergers, which are multimessenger astronomical events that have been observed both in gravitational waves and in the multiband electromagnetic spectrum [1]. Depending on the masses of the stars in the binary and on details of their largely unknown equation of state, a dynamically evolving and short-lived neutron star may be formed after the merger, existing for approximately 10-300 ms before collapsing to a black hole [2, 3]. Numerical relativity simulations across different groups consistently show broad power spectral features in the 1-5 kHz range in the post-merger gravitational wave signal [4–14], which is inaccessible by current gravitational-wave detectors but could be seen by future third generation ground-based detectors in the next decade [15–17]. This implies the possibility of quasiperiodic modulation of the emitted γ-rays in a subset of events where a neutron star is formed shortly prior to the final collapse to a black hole [18–21]. Here we present two such signals identified in the short bursts GRB 910711 and GRB 931101B from archival BATSE data, which are compatible with the predictions from numerical relativity. Copyright © 2023, The Authors. All rights reserved.

关键词： Gravity waves

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Lattice QCD Study of Transverse-Momentum Dependent Soft Function

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Physical Review Letters 2022年第6期128卷 062002-062002页

作者： Yuan Li Shi-Cheng Xia Constantia Alexandrou Krzysztof Cichy Martha Constantinou Xu Feng Kyriakos Hadjiyiannakou Karl Jansen Chuan Liu Aurora Scapellato Fernanda Steffens Jacopo Tarello School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China Department of Physics University of Cyprus P.O. Box 20537 1678 Nicosia Cyprus Computation-based Science and Technology Research Center The Cyprus Institute 20 Kavafi Str. Nicosia 2121 Cyprus Faculty of Physics Adam Mickiewicz University ul. Uniwersytetu Poznańskiego 2 61-614 Poznań Poland Temple University 1925 N. 12th Street Philadelphia Pennsylvania 19122-1801 USA Collaborative Innovation Center of Quantum Matter Beijing 100871 China Center for High Energy Physics Peking University Beijing 100871 China NIC DESY Platanenallee 6 D-15738 Zeuthen Germany Institut für Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nussallee 14-16 53115 Bonn Germany

In this work, we perform a lattice QCD study of the intrinsic, rapidity-independent soft function within the framework of large momentum effective theory. The computation is carried out using a gauge ensemble of Nf=2+1+1 clover-improved twisted mass fermion. After applying an appropriate renormalization procedure and the removal of significant higher-twist contamination, we obtain the intrinsic soft function that is comparable to the one-loop perturbative result at large external momentum. The determination of the nonperturbative soft function from first principles is crucial to sharpen our understanding of the processes with small transverse momentum such as the Drell-Yan production and the semi-inclusive deep inelastic scattering. Additionally, we calculate the Collins-Soper evolution kernel using the quasi-transverse-momentum-dependent wave function as input.

关键词： Lattice QCD Lattice gauge theory

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Spinful Topological Phases in Acoustic Crystals with Projective PT Symmetry

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Physical Review Letters 2023年第2期130卷 026101-026101页

作者： Yan Meng Shuxin Lin Bin-jie Shi Bin Wei Linyun Yang Bei Yan Zhenxiao Zhu Xiang Xi Yin Wang Yong Ge Shou-qi Yuan Jingming Chen Gui-Geng Liu Hong-xiang Sun Hongsheng Chen Yihao Yang Zhen Gao Department of Electrical and Electronic Engineering Southern University of Science and Technology Shenzhen 518055 China Research Center of Fluid Machinery Engineering and Technology School of Physics and Electronics Engineering Jiangsu University Zhenjiang 212013 China SKLSM Institute of Semiconductors Chinese Academy of Sciences Beijing 100083 China Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China Division of Physics and Applied Physics School of Physical and Mathematical Sciences Nanyang Technological University 21 Nanyang Link Singapore 637371 Singapore State Key Laboratory of Acoustics Institute of Acoustics Chinese Academy of Sciences Beijing 100190 China Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and Instrumentation ZJU-Hangzhou Global Scientific and Technological Innovation Center Zhejiang University Hangzhou 310027 China International Joint Innovation Center The Electromagnetics Academy at Zhejiang University Zhejiang University Haining 314400 China Key Lab. of Advanced Micro/Nano Electronic Devices & Smart Systems of Zhejiang Jinhua Institute of Zhejiang University Zhejiang University Jinhua 321099 China Shaoxing Institute of Zhejiang University Zhejiang University Shaoxing 312000 China

For the classification of topological phases of matter, an important consideration is whether a system is spinless or spinful, as these two classes have distinct symmetry algebra that gives rise to fundamentally different topological phases. However, only recently has it been realized theoretically that in the presence of gauge symmetry, the algebraic structure of symmetries can be projectively represented, which possibly enables the switch between spinless and spinful topological phases. Here, we report the experimental demonstration of this idea by realizing spinful topological phases in “spinless” acoustic crystals with projective space-time inversion symmetry. In particular, we realize a one-dimensional topologically gapped phase characterized by a 2Z winding number, which features double-degenerate bands in the entire Brillouin zone and two pairs of degenerate topological boundary modes. Our Letter thus overcomes a fundamental constraint on topological phases by spin classes.

关键词： Acoustics Edge states Topological insulators 1-dimensional systems Finite-element method Gauge symmetries Projective symmetries Tight-binding model

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