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Bell Nonlocality in Classical Systems Coexisting with Other System Types

Physical Review Letters 2024年第19期132卷 190201-190201页

作者： Giulio Chiribella Lorenzo Giannelli Carlo Maria Scandolo QICI Quantum Information and Computation Initiative Department of Computer Science The University of Hong Kong Pok Fu Lam Road Hong Kong Quantum Group Department of Computer Science University of Oxford Wolfson Building Parks Road Oxford United Kingdom Perimeter Institute for Theoretical Physics 31 Caroline Street North Waterloo Ontario Canada HKU-Oxford Joint Laboratory for Quantum Information and Computation Department of Mathematics and Statistics University of Calgary 2500 University Drive NW Calgary Alberta Canada Institute for Quantum Science and Technology University of Calgary 2500 University Drive NW Calgary Alberta Canada

The realistic interpretation of classical theory assumes that every classical system has well-defined properties, which may be unknown to the observer but are nevertheless part of reality and can, in principle, be revealed by measurements. Here we show that this interpretation can, in principle, be falsified if classical systems coexist with other types of physical systems. To make this point, we construct a toy theory that (i) includes classical theory as a subtheory and (ii) allows classical systems to be entangled with another type of system, called anticlassical. We show that our toy theory allows for the violation of Bell inequalities in two-party scenarios where one of the settings corresponds to a local measurement performed on a classical system alone. Building on this fact, we show that measurement outcomes in classical theory cannot, in general, be regarded as predetermined by the state of an underlying reality.

关键词： Quantum correlations, foundations & formalism Quantum formalism Quantum foundations

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Ultrafast and electrically tunable Rabi frequency in a germanium hut wire hole spin qubit

arXiv

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arXiv 2023年

作者： Liu, He Wang, Ke Gao, Fei Leng, Jin Liu, Yang Zhou, Yu-Chen Cao, Gang Wang, Ting Zhang, Jianjun Huang, Peihao Li, Hai-Ou Guo, Guo-Ping CAS Key Laboratory of Quantum Information University of Science and Technology of China Anhui Hefei230026 China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Anhui Hefei230026 China Institute of Physics CAS Center for Excellence in Topological Quantum Computation Chinese Academy of Sciences Beijing100190 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China International Quantum Academy Shenzhen518048 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Qilu Institute of Technology Jinan250200 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China Origin Quantum Computing Company Limited Anhui Hefei230026 China

Hole spin qubits based on germanium (Ge) have strong tunable spin orbit interaction (SOI) and ultrafast qubit operation speed. Here we report that the Rabi frequency (fRabi) of a hole spin qubit in a Ge hut wire (HW) double quantum dot (DQD) is electrically tuned through the detuning energy (ϵ) and middle gate voltage (VM ). fRabi gradually decreases with increasing ϵ;on the contrary, fRabi is positively correlated with VM. We attribute our results to the change of electric field on SOI and the contribution of the excited state in quantum dots to fRabi. We further demonstrate an ultrafast fRabi exceeding 1.2 GHz, which evidences the strong SOI in our device. The discovery of an ultrafast and electrically tunable fRabi in a hole spin qubit has potential applications in semiconductor quantum computing. Copyright © 2023, The Authors. All rights reserved.

关键词： Germanium

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Optical telecommunications-band clock based on neutral titanium atoms

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Physical Review A 2023年第5期107卷 L051102-L051102页

作者： Scott Eustice Dmytro Filin Jackson Schrott Sergey Porsev Charles Cheung Diego Novoa Dan M. Stamper-Kurn Marianna S. Safronova Department of Physics University of California Berkeley California 94720 USA Challenge Institute for Quantum Computation University of California Berkeley California 94720 USA Department of Physics and Astronomy University of Delaware Newark Delaware 19716 USA Materials Science Division Lawrence Berkeley National Laboratory Berkeley California 94720 USA Joint Quantum Institute National Institute of Standards and Technology and the University of Maryland College Park Maryland 20742 USA

We propose an optical clock based on ultranarrow transitions in neutral titanium, which exhibit small blackbody radiation and quadratic Zeeman shifts and have wavelengths in the S-, C-, and L-telecommunications fiber bands, allowing for integration with robust laser technology. We calculate relevant properties using a high-precision relativistic hybrid method that combines configuration interaction and coupled-cluster approaches. To identify magic wavelengths, we have completed the largest-to-date direct dynamical polarizability calculations. Finally, we identify challenges that arise from magnetic dipole-dipole interactions and describe an approach to overcome them. A telecommunications-band atomic frequency standard will aid the deployment of optical clock networks and clock comparisons over long distances.

关键词： Atomic, optical & lattice clocks Electron correlation calculations for atoms & ions Electronic transitions Exotic atoms & molecules Polarizability Configuration interaction Coupled cluster

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Δ(1232) Axial Charge and Form Factors from Lattice QCD

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Physical Review Letters 2011年第14期107卷 141601-141601页

作者： Constantia Alexandrou Eric B. Gregory Tomasz Korzec Giannis Koutsou John W. Negele Toru Sato Antonios Tsapalis Department of Physics University of Cyprus P.O. Box 20357 1678 Nicosia Cyprus Computation-based Science and Technology Research Center The Cyprus Institute P.O. Box 27456 1645 Nicosia Cyprus Institut für Physik Humboldt Universität zu Berlin Newtonstrasse 15 12489 Berlin Germany Center for Theoretical Physics Laboratory for Nuclear Science and Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Department of Physics Osaka University Osaka 560-0043 Japan Hellenic Naval Academy Hatzikyriakou Avenue Pireaus 18539 Greece Department of Physics National Technical University of Athens Zografou Campus 15780 Athens Greece

We present the first calculation on the Δ axial vector and pseudoscalar form factors using lattice QCD. Two Goldberger-Treiman relations are derived and examined. A combined chiral fit is performed to the nucleon axi... 详细信息

关键词： FORM factor (Nuclear physics) QUANTUM chromodynamics LATTICE theory HADRON spectroscopy COUPLING constants (Nuclear physics)

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Representation matching for remote quantum computing

arXiv

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arXiv 2020年

作者： Yang, Yuxiang Hayashi, Masahito Institute for Theoretical Physics ETH Zürich QICI Quantum Information and Computation Initiative Department of Computer Science University of Hong Kong Pokfulam Road Hong Kong Hong Kong Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Graduate School of Mathematics Nagoya University Nagoya464-8602 Japan

Many quantum computational tasks have inherent symmetries, suggesting a path to enhancing their efficiency and performance. Exploiting this observation, we propose representation matching, a generic probabilistic protocol for reducing the cost of quantum computation in a quantum network. We show that the representation matching protocol is capable of reducing the communication or memory cost to almost minimum in various tasks, including remote execution of unitary gate arrays, permutation gates and unitary conjugation, as well as the storage and retrieval of unitary gates. Copyright © 2020, The Authors. All rights reserved.

关键词： Cost reduction

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Theory for Magnetic-Field-Driven 3D Metal-Insulator Transitions in the Quantum Limit

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Physical Review Letters 2021年第4期127卷 046602-046602页

作者： Peng-Lu Zhao 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

Metal-insulator transitions driven by magnetic fields have been extensively studied in 2D, but a 3D theory is still lacking. Motivated by recent experiments, we develop a scaling theory for the metal-insulator transitions in the strong-magnetic-field quantum limit of a 3D system. By using a renormalization-group calculation to treat electron-electron interactions, electron-phonon interactions, and disorder on the same footing, we obtain the critical exponent that characterizes the scaling relations of the resistivity to temperature and magnetic field. By comparing the critical exponent with those in a recent experiment [F. Tang et al., Nature (London) 569, 537 (2019)], we conclude that the insulating ground state was not only a charge-density wave driven by electron-phonon interactions but also coexisting with strong electron-electron interactions and backscattering disorder. We also propose a current-scaling experiment for further verification. Our theory will be helpful for exploring the emergent territory of 3D metal-insulator transitions under strong magnetic fields.

关键词： Charge density waves Critical exponents Critical field Quantum transport Topological insulators

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Quantum microscopy with van der Waals heterostructures

arXiv

引用

arXiv 2021年

作者： Healey, A.J. Scholten, S.C. Yang, T. Scott, J.A. Abrahams, G.J. Robertson, I.O. Hou, X.F. Guo, Y.F. Rahman, S. Lu, Y. Kianinia, M. Aharonovich, I. Tetienne, Jean-Philippe School of Physics University of Melbourne VIC3010 Australia Centre for Quantum Computation and Communication Technology School of Physics University of Melbourne VIC3010 Australia School of Mathematical and Physical Sciences University of Technology Sydney UltimoNSW2007 Australia ARC Centre of Excellence for Transformative Meta-Optical Systems University of Technology Sydney UltimoNSW2007 Australia School of Science RMIT University MelbourneVIC3001 Australia School of Physical Science and Technology ShanghaiTech University Shanghai201210 China ShanghaiTech Laboratory for Topological Physics ShanghaiTech University Shanghai201210 China School of Engineering College of Engineering & Computer Science Australian National University CanberraACT2601 Australia Centre for Quantum Computation and Communication Technology Australian National University CanberraACT2601 Australia

Quantum microscopes based on solid-state spin quantum sensors have recently emerged as powerful tools for probing material properties and physical processes in regimes not accessible to classical sensors, especially on the nanoscale [1-4]. Such microscopes have already found utility in a variety of problems, from imaging magnetism and charge transport in nanoscale devices [5-10], to mapping remanent magnetic fields from ancient rocks and biological organisms [11-13]. However, applications of quantum microscopes have so far relied on sensors hosted in a rigid, three-dimensional crystal, typically diamond, which limits their ability to closely interact with the sample under study. Here we demonstrate a versatile and robust quantum microscope using quantum sensors embedded within a thin layer of a van der Waals (vdW) material, hexagonal boron nitride (hBN). To showcase the capabilities of this platform, we assemble several active vdW heterostructures, with an hBN layer acting as the quantum sensor. We demonstrate time-resolved, simultaneous temperature and magnetic imaging near the Curie temperature of a vdW ferromagnet as well as apply this unique microscope to map out charge currents and Joule heating in graphene. By enabling intimate proximity between sensor and sample, potentially down to a single atomic layer, the hBN quantum sensor represents a paradigm shift for nanoscale quantum sensing and microscopy. Moreover, given the ubiquitous use of hBN in modern materials and condensed matter physics research [14, 15], we expect our technique to find rapid and broad adoption in these fields, further motivated by the prospect of performing in-situ chemical analysis and noise spectroscopy using advanced quantum sensing protocols [16-19]. Copyright © 2021, The Authors. All rights reserved.

关键词： Van der Waals forces

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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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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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