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arXiv 2018年

作者： Xu, Xiao Yan Qi, Yang Zhang, Long Assaad, Fakher F. Xu, Cenke Meng, Zi Yang Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong Hong Kong Center for Field Theory and Particle Physics Department of Physics Fudan University Shanghai200433 China State Key Laboratory of Surface Physics Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China Kavli Institute for Theoretical Sciences CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China Institut für Theoretische Physik und Astrophysik Universität Würzburg Würzburg97074 Germany Department of Physics University of California Santa BarbaraCA93106 United States Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing100190 China Department of Physics University of Hong Kong China CAS Center of Excellence in Topological Quantum Computation and School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Songshan Lake Materials Laboratory DongguanGuangdong523808 China

The interplay between lattice gauge theories and fermionic matter accounts for fundamental physical phenomena ranging from the deconfinement of quarks in particle physics to quantum spin liquid with fractionalized anyons and emergent gauge structures in condensed matter physics. However, except for certain limits (for instance large number of flavors of matter fields), analytical methods can provide few concrete results. Here we show that the problem of compact U(1) lattice gauge theory coupled to fermionic matter in (2 + 1)D is possible to access via sign-problem-free quantum Monte Carlo simulations. One can hence map out the phase diagram as a function of fermion flavors and the strength of gauge fluctuations. By increasing the coupling constant of the gauge field, gauge confinement in the form of various spontaneous symmetry breaking phases such as valence bond solid (VBS) and Néel antiferromagnet emerge. Deconfined phases with algebraic spin and VBS correlation functions are also observed. Such deconfined phases are incarnation of an exotic states of matter, i.e. the algebraic spin liquid, which is generally viewed as the parent state of various quantum phases. The phase transitions between deconfined and confined phases, as well as that between the different confined phases provide various manifestations of deconfined quantum criticality. In particular, for four flavors, Nf = 4, our data suggests a continuous quantum phase transition between the VBS and Néel order. We also provide preliminary theoretical analysis for these quantum phase transitions. Copyright © 2018, The Authors. All rights reserved.

关键词： Phase transitions

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Radiation tolerance of two-dimensional material-based devices for space applications

arXiv

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arXiv 2018年

作者： Vogl, Tobias Sripathy, Kabilan Sharma, Ankur Reddy, Prithvi Sullivan, James Machacek, Joshua R. Zhang, Linglong Karouta, Fouad Buchler, Ben C. Doherty, Marcus W. Lu, Yuerui Lam, Ping Koy Centre for Quantum Computation and Communication Technology Department of Quantum Science Research School of Physics and Engineering Australian National University ActonACT2601 Australia Research School of Engineering Australian National University ActonACT2601 Australia Laser Physics Centre Research School of Physics and Engineering Australian National University ActonACT2601 Australia Plasma Research Laboratory Research School of Physics and Engineering Australian National University CanberraACT2601 Australia Australian National Fabrication Facility Research School of Physics and Engineering Australian National University ActonACT2601 Australia

Characteristic for devices based on two-dimensional materials are their low size, weight and power requirements. This makes them advantageous for use in space instrumentation, including photovoltaics, batteries, electronics, sensors and light sources for long-distance quantum communication. Here, we present for the first time a comprehensive study on combined radiation effects in earth’s atmosphere on various devices based on these nanomaterials. Using theoretical modeling packages, we estimate relevant radiation levels and then expose field-effect transistors, single-photon sources and monolayers as building blocks for future electronics to gamma-rays, protons and electrons. The devices show negligible change in performance after the irradiation, suggesting robust suitability for space use. Under excessive γ-radiation, however, monolayer WS2 showed decreased defect densities, identified by an increase in photoluminescence, carrier lifetime and a change in doping ratio proportional to the photon flux. The underlying mechanism was traced back to radiation-induced defect healing, wherein dissociated oxygen passivates sulfur vacancies. Copyright © 2018, The Authors. All rights reserved.

关键词： Monolayers

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Multi-messenger astrophysics: Harnessing the data revolution

arXiv

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arXiv 2018年

作者： Allen, Gabrielle Anderson, Warren Blaufuss, Erik Bloom, Joshua S. Brady, Patrick Burke-Spolaor, Sarah Bradley Cenko, S. Connolly, Andrew Couvares, Peter Fox, Derek Gal-Yam, Avishay Gezari, Suvi Goodman, Alyssa Grant, Darren Groot, Paul Guillochon, James Hanna, Chad Hogg, David W. Holley-Bockelmann, Kelly Andrew Howell, D. Kaplan, David Katsavounidis, Erik Kowalski, Marek Lehner, Luis Muthukrishna, Daniel Narayan, Gautham Peek, J.E.G. Saha, Abhijit Shawhan, Peter Taboada, Ignacio National Center for Supercomputing Applications University of Illinois at Urbana-Champaign Center for Gravitation Cosmology and Astrophysics University of Wisconsin-Milwaukee Department of Physics University of Maryland Department of Astronomy University of California Berkeley United States Department of Physics and Astronomy West Virginia University Center for Gravitational Waves and Astronomy West Virginia University NASA Goddard Space Flight Center Joint Space-Science Institute Department of Astronomy University of Washington LIGO Laboratory California Institute of Technology Department of Astronomy and Astrophysics Pennsylvania State University Department of Particle Physics and Astrophysics Weizmann Institute of Science Department of Astronomy University of Maryland Harvard-Smithsonian Center for Astrophysics Department of Physics University of Alberta Department of Astrophysics Radboud University Institute for Theory and Computation Harvard-Smithsonian Center for Astrophysics Department of Physics Pennsylvania State University Center for Cosmology and Particle Physics New York University Center for Computational Astrophysics Flatiron Institute Department of Physics and Astronomy Vanderbilt University Las Cumbres Observatory Department of Physics University of California Santa Barbara United States LIGO Laboratory Massachusetts Institute of Technology Institute of Physics Humboldt University of Berlin Perimeter Institute for Theoretical Physics Institute of Astronomy University of Cambridge Space Telescope Science Institute Johns Hopkins University School of Physics Georgia Institute of Technology

The past year has witnessed discovery of the first identified counterparts to a gravitational wave transient (GW 170817A) and a very high-energy neutrino (IceCube-170922A). These source identifications, and ensuing detailed studies, have realized longstanding dreams of astronomers and physicists to routinely carry out observations of cosmic sources by other than electromagnetic means, and inaugurated the era of "multi-messenger" astronomy. While this new era promises extraordinary physical insights into the universe, it brings with it new challenges, including: highly heterogeneous, high-volume, high-velocity datasets;globe-spanning cross-disciplinary teams of researchers, regularly brought together into transient collaborations;an extraordinary breadth and depth of domain-specific knowledge and computing resources required to anticipate, model, and interpret observations;and the routine need for adaptive, distributed, rapid-response observing campaigns to fully exploit the scientific potential of each source. We argue, therefore, that the time is ripe for the community to conceive and propose an Institute for Multi-Messenger Astrophysics that would coordinate its resources in a sustained and strategic fashion to efficiently address these challenges, while simultaneously serving as a center for education and key supporting activities. In this fashion, we can prepare now to realize the bright future that we see, beyond, through these newly opened windows onto the universe. Copyright © 2018, The Authors. All rights reserved.

关键词： Domain Knowledge

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Calculating the ρ radiative decay width with lattice QCD

arXiv

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arXiv 2018年

作者： Leskovec, Luka Alexandrou, Constantia Meinel, Stefan Negele, John W. Paul, Srijit Petschlies, Marcus Pochinsky, Andrew Rendon, Gumaro Syritsyn, Sergey Thomas Jefferson National Accelerator Facility 12000 Jefferson Avenue Newport NewsVA23606 United States Department of Physics University of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Street Nicosia2121 Cyprus Department of Physics University of Arizona TucsonAZ85721 United States RIKEN BNL Research Center Brookhaven National Laboratory UptonNY11973 United States Center for Theoretical Physics Laboratory for Nuclear Science Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Helmholtz-Institut für Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nußallee 14-16 BonnD-53115 Germany Department of Physics and Astronomy Stony Brook University Stony BrookNY11794 United States

We present the results of our lattice QCD study of the πγ → ππ process, where the ρ resonance appears as an enhancement in the transition amplitude. We use Nf = 2 + 1 clover fermions on a lattice of L = 3.6 fm and a pion mass of 320 MeV. Using a combination of forward, stochastic, and sequential propagators, we calculate the two-point and three-point functions that allow us to determine the πγ → ππ matrix elements for several values of the invariant mass s and momentum transfer q2. To fit the q2 and s dependence of the πγ → ππ amplitude, we explore a set of general parametrizations based on a Taylor expansion. By analytic continuation to the complex pole corresponding to the ρ resonance, we determine the resonant form factors and calculate the radiative decay width of the ρ. Copyright © 2018, The Authors. All rights reserved.

关键词： Quantum theory

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Charge-density-wave transitions of Dirac fermions coupled to phonons

arXiv

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arXiv 2018年

作者： Chen, Chuang Xu, Xiao Yan Meng, Zi Yang Hohenadler, Martin Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Department of Physics Hong Kong University of Science and Technology Clear Water Bay Hong Kong Hong Kong CAS Center of Excellence in Topological Quantum Computation School of Physical Sciences University of Chinese Academy of Sciences Beijing100190 China Songshan Lake Materials Laboratory Dongguan Guangdong523808 China Institut für Theoretische Physik und Astrophysik Universität Würzburg Würzburg97074 Germany

The spontaneous generation of charge-density-wave order in a Dirac fermion system via the natural mechanism of electron-phonon coupling is studied in the framework of the Holstein model on the honeycomb lattice. Using two independent and unbiased quantum Monte Carlo methods, the phase diagram as a function of temperature and coupling strength is determined. It features a quantum critical point as well as a line of thermal critical points. Finite-size scaling appears consistent with fermionic Gross-Neveu-Ising universality for the quantum phase transition, and bosonic Ising universality for the thermal phase transition. The critical temperature has a maximum at intermediate couplings. Our findings motivate experimental efforts to identify or engineer Dirac systems with sufficiently strong and tunable electron-phonon coupling. Copyright © 2018, The Authors. All rights reserved.

关键词： Charge density

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Experimental Observation of One-Dimensional Superradiance Lattices in Ultracold Atoms

引用

Physical Review Letters 2018年第19期120卷 193601-193601页

作者： Liangchao Chen Pengjun Wang Zengming Meng Lianghui Huang Han Cai Da-Wei Wang Shi-Yao Zhu Jing Zhang State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Opto-Electronics Shanxi University Taiyuan 030006 People’s Republic of China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan 030006 People’s Republic of China Interdisciplinary Center of Quantum Information and Department of Physics Zhejiang University Hangzhou 310027 People’s Republic of China Institute of Quantum Science and Engineering Texas A&M University College Station Texas 77843 USA CAS Center of Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 People’s Republic of China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 People’s Republic of China

We measure the superradiant emission in a one-dimensional (1D) superradiance lattice (SL) in ultracold atoms. Resonantly excited to a superradiant state, the atoms are further coupled to other collectively excited states, which form a 1D SL. The directional emission of one of the superradiant excited states in the 1D SL is measured. The emission spectra depend on the band structure, which can be controlled by the frequency and intensity of the coupling laser fields. This work provides a platform for investigating the collective Lamb shift of resonantly excited superradiant states in Bose-Einstein condensates and paves the way for realizing higher dimensional superradiance lattices.

关键词： Collective effects in quantum optics Superradiance & subradiance

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Log-periodic quantum magneto-oscillations and discrete scale invariance in topological material HfTe5

arXiv

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arXiv 2018年

作者： Wang, Huichao Liu, Yanzhao Liu, Yongjie Xi, Chuanying Wang, Junfeng Liu, Jun Wang, Yong Li, Liang Lau, Shu Ping Tian, Mingliang Yan, Jiaqiang Mandrus, David Dai, Ji-Yan Liu, Haiwen Xie, X.C. Wang, Jian International Center for Quantum Materials School of Physics Peking University Beijing100871 China Department of Applied Physics Hong Kong Polytechnic University Kowloon Hong Kong Wuhan National High Magnetic Field Center Huazhong University of Science and Technology Wuhan430074 China High Magnetic Field Laboratory Chinese Academy of Sciences HefeiAnhui230031 China Center of Electron Microscopy State Key Laboratory of Silicon Materials School of Materials Science and Engineering Zhejiang University Hangzhou310027 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 Collaborative Innovation Center of Quantum Matter Beijing100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing100190 China

Discrete scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity which can be rarely observed in quantum systems. Here we report the log-periodic quantum oscillations in the magnetoresistance (MR) and the Hall traces of HfTe5 crystals, which reveals the appearance of DSI. The oscillations show the same logB-periodicity in the behavior of MR and Hall, indicating an overall effect of the DSI on the transport properties. Moreover, the DSI feature in the Hall resistance signals its close relation to the carriers. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. Our work evidences the universality of the DSI in the Dirac materials and paves way for the full understanding of the novel phenomenon. Copyright © 2018, The Authors. All rights reserved.

关键词： Tellurium compounds

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Simultaneous continuous measurement of noncommuting observables: Quantum state correlations

引用

Physical Review A 2018年第1期97卷 012118-012118页

作者： Areeya Chantasri Juan Atalaya Shay Hacohen-Gourgy Leigh S. Martin Irfan Siddiqi Andrew N. Jordan Department of Physics and Astronomy University of Rochester Rochester New York 14627 USA Center for Coherence and Quantum Optics University of Rochester Rochester New York 14627 USA Centre for Quantum Computation and Communication Technology (Australian Research Council) Centre for Quantum Dynamics Griffith University Nathan QLD 4111 Australia Department of Electrical Engineering University of California Riverside California 92521 USA Quantum Nanoelectronics Laboratory Department of Physics University of California Berkeley California 94720 USA Center for Quantum Coherent Science University of California Berkeley California 94720 USA Institute for Quantum Studies Chapman University 1 University Drive Orange California 92866 USA

We consider the temporal correlations of the quantum state of a qubit subject to simultaneous continuous measurement of two noncommuting qubit observables. Such qubit state correlators are defined for an ensemble of qubit trajectories, which has the same fixed initial state and can also be optionally constrained by a fixed final state. We develop a stochastic path integral description for the continuous quantum measurement and use it to calculate the considered correlators. Exact analytic results are possible in the case of ideal measurements of equal strength and are also shown to agree with solutions obtained using the Fokker-Planck equation. For a more general case with decoherence effects and inefficiency, we use a diagrammatic approach to find the correlators perturbatively in the quantum efficiency. We also calculate the state correlators for the quantum trajectories which are extracted from readout signals measured in a transmon qubit experiment, by means of the quantum Bayesian state update. We find an excellent agreement between the correlators based on the experimental data and those obtained from our analytical and numerical results.

关键词： Open quantum systems & decoherence Quantum foundations Quantum measurements Weak values & weak measurements Stochastic analysis Stochastic processes & statistics

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High precision optical AC magnetometry using dynamical decoupling

arXiv

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arXiv 2018年

作者： Gupta, Manish K. Kunjummen, Jonathan Wang, Xiaoting Dowling, Jonathan P. Quantum Information and Computation Group Harish-Chandra Research Institute HBNI Chhatnag Road Jhunsi Allahabad Uttar Pradesh211019 India Hearne Institute for Theoretical Physics Department of Physics and Astronomy Louisiana State University Baton RougeLA70803 United States Homer L. Dodge Department of Physics and Astronomy University of Oklahoma NormanOK73019 United States Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu610054 China CAS-Alibaba Quantum Computing Laboratory USTC Shanghai201315 China NYU-ECNU Institute of Physics NYU Shanghai Shanghai200062 China National Institute of Information and Communications Technology 4-2-1 Nukui-Kitamachi Koganei Tokyo184-8795 Japan

We propose a magnetometer for the precise measurement of AC magnetic fields that uses a Terbium-doped optical fiber with half-waveplates built into it at specified distances. Our scheme uses an open-loop quantum control technique called dynamical decoupling to reduce the noise floor and thus increase the sensitivity. We show that dynamical decoupling is extremely effective in preserving the photon state evolution due to the external AC magnetic field from random birefringence in the fiber, even when accounting for errors in pulse timing. Hence we achieve high sensitivity. For a given inter-waveplate distance, the minimum detectable field is inversely proportional to fiber length, as is the bandwidth of detectable frequencies. Copyright © 2018, The Authors. All rights reserved.

关键词： Optical fibers

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Origins of diamond surface noise probed by correlating single spin measurements with surface spectroscopy

arXiv

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arXiv 2018年

作者： Sangtawesin, Sorawis Dwyer, Bo L. Srinivasan, Srikanth Allred, James J. Rodgers, Lila V.H. de Greve, Kristiaan Stacey, Alastair Dontschuk, Nikolai O’Donnell, Kane M. Hu, Di Andrew Evans, D. Jaye, Cherno Fischer, Daniel A. Markham, Matthew L. Twitchen, Daniel J. Park, Hongkun Lukin, Mikhail D. de Leon, Nathalie P. Department of Electrical Engineering Princeton University PrincetonNJ08544 United States Department of Physics Harvard University CambridgeMA02138 United States Centre for Quantum Computation and Communication Technology School of Physics University of Melbourne ParkvilleVIC3010 Australia Department of Physics Astronomy and Medical Radiation Science Curtin University BentleyWA Australia Department of Physics Aberystwyth University AberystwythSY23 3BZ United Kingdom Material Measurement Laboratory National Institute of Standards and Technology GaithersburgMD20899 United States Element Six HarwellOX11 0QR United Kingdom Department of Chemistry and Chemical Biology Harvard University CambridgeMA02138 United States

The nitrogen vacancy (NV) center in diamond exhibits spin-dependent fluorescence and long spin coherence times under ambient conditions, enabling applications in quantum information processing and sensing 1, 2. NV centers near the surface can have strong interactions with external materials and spins, enabling new forms of nanoscale spectroscopy 3–6. However, NV spin coherence degrades within 100 nanometers of the surface, suggesting that diamond surfaces are plagued with ubiquitous defects 7–10. Prior work on characterizing near-surface noise has primarily relied on using NV centers themselves as probes 7–12;while this has the advantage of exquisite sensitivity, it provides only indirect information about the origin of the noise. Here we demonstrate that surface spectroscopy methods and single spin measurements can be used as complementary diagnostics to understand sources of noise. We find that surface morphology is crucial for realizing reproducible chemical termination, and use these insights to achieve a highly ordered, oxygen-terminated surface with suppressed noise. We observe NV centers within 10 nm of the surface with coherence times extended by an order of magnitude. Copyright © 2018, The Authors. All rights reserved.

关键词： Spectroscopic analysis

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