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Second-Order Perturbation in Adaptive Perturbation Method

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arXiv 2020年

作者： Ma, Chen-Te Asia Pacific Center for Theoretical Physics Pohang University of Science and Technology Gyeongsangbuk-do Pohang37673 Korea Republic of Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangdong Guangzhou510006 China School of Physics and Telecommunication Engineering South China Normal University Guangdong Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangdong Guangzhou510006 China The Laboratory for Quantum Gravity and Strings Department of Mathematics and Applied Mathematics University of Cape Town Private Bag Rondebosch7700 South Africa

The perturbation method is an approximation scheme with a solvable leading order. The standard way is to choose a non-interacting sector for the leading order. The adaptive perturbation method improves the solvable part by using all diagonal elements for a Fock state. We consider the harmonic oscillator with the interacting term, λ1x4/6 + λ2x6/120, where λ1 and λ2 are coupling constants, and x is the position operator. The spectrum shows a quantitative result from the second-order, less than 1 percent error, compared to a numerical solution when turning off the λ2. When we turn on the λ2, more deviation occurs, but the error is still less than 2 percent. We show a quantitative result beyond a weak-coupling region. Our study should provide interest in the holographic principle and strongly coupled boundary theory. Copyright © 2020, The Authors. All rights reserved.

关键词： Perturbation techniques

quantum invariants and the graph isomorphism problem

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Physical Review A 2019年第5期100卷 052317-052317页

作者： P. W. Mills R. P. Rundle J. H. Samson Simon J. Devitt Todd Tilma V. M. Dwyer Mark J. Everitt Quantum Systems Engineering Research Group Department of Physics Loughborough University Leicestershire LE11 3TU United Kingdom The Wolfson School Loughborough University Loughborough Leicestershire LE11 3TU England United Kingdom Centre for Quantum Software and Information Faculty of Engineering and Information Technology University of Technology Sydney Sydney NSW 2007 Australia Turing Inc. Berkeley California 94701 USA Department of Physics College of Science Tokyo Institute of Technology H-63 2-12-1 Oookayama Meguro-ku Tokyo 152-8550 Japan Quantum Computing Unit Institute of Innovative Research Tokyo Institute of Technology S1-16 4259 Nagatsuta-cho Midori-ku Yokohama 226-8503 Japan

Three graph invariants are introduced which may be measured from a quantum graph state and form examples of a framework under which other graph invariants can be constructed. Each invariant is based on distinguishing a different number of qubits. This is done by applying different measurements to the qubits to be distinguished. The performance of these invariants is evaluated and compared to classical invariants. We verify that the invariants can distinguish all nonisomorphic graphs with nine or fewer nodes. The invariants have also been applied to “classically hard” strongly regular graphs, successfully distinguishing all strongly regular graphs of up to 29 nodes, and preliminarily to weighted graphs. We have found that, although it is possible to prepare states with a polynomial number of operations, the average number of preparations required to distinguish nonisomorphic graph states scales exponentially with the number of nodes. We have so far been unable to find operators which reliably compare graphs and reduce the required number of preparations to feasible levels.

关键词： quantum algorithms Graph theory Phase space methods

Application of a resource theory of channels to communication scenarios

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arXiv 2019年

作者： Takagi, Ryuji Wang, Kun Hayashi, Masahito Center for Theoretical Physics Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518000 China Graduate School of Mathematics Nagoya University Nagoya464-8602 Japan Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 117542 Singapore

We introduce a resource theory of channels relevant to communication via quantum channels, in which the set of constant channels, useless channels for communication tasks, are considered as free resources. We find that our theory with such a simple structure is useful to address important problems in quantum Shannon theory — in particular, we provide a converse bound for the one-shot non-signalling assisted classical capacity that leads to the first direct proof of the strong converse property for non-signalling assisted communication, as well as obtain the one-shot channel simulation cost with non-signalling assistance. Our results not only provide new perspectives to those problems, but also admit concise proofs of them, connecting the recently developed fields of resource theories to ‘classic’ problems in quantum information theory and shedding light on the validity of resource theories of channels as effective tools to attack practical problems. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum optics

Limits on sub-GeV dark matter from the PROSPECT reactor antineutrino experiment

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Physical Review D 2021年第1期104卷 012009-012009页

作者： M. Andriamirado A. B. Balantekin H. R. Band C. D. Bass D. E. Bergeron N. S. Bowden C. D. Bryan T. Classen A. J. Conant G. Deichert M. V. Diwan M. J. Dolinski A. Erickson B. T. Foust J. K. Gaison A. Galindo-Uribarri C. E. Gilbert S. Hans A. B. Hansell K. M. Heeger B. Heffron D. E. Jaffe S. Jayakumar X. Ji D. C. Jones J. Koblanski O. Kyzylova C. E. Lane T. J. Langford J. LaRosa B. R. Littlejohn X. Lu J. Maricic M. P. Mendenhall A. M. Meyer R. Milincic P. E. Mueller H. P. Mumm J. Napolitano R. Neilson J. A. Nikkel S. Nour J. L. Palomino D. A. Pushin X. Qian R. Rosero P. T. Surukuchi M. A. Tyra R. L. Varner D. Venegas-Vargas P. B. Weatherly C. White J. Wilhelmi A. Woolverton M. Yeh C. Zhang X. Zhang Christopher V. Cappiello Department of Physics Illinois Institute of Technology Chicago Illinois USA Department of Physics University of Wisconsin Madison Wisconsin USA Wright Laboratory Department of Physics Yale University New Haven Connecticut USA Department of Physics Le Moyne College Syracuse New York USA National Institute of Standards and Technology Gaithersburg Maryland USA Nuclear and Chemical Sciences Division Lawrence Livermore National Laboratory Livermore California USA High Flux Isotope Reactor Oak Ridge National Laboratory Oak Ridge Tennessee USA George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Atlanta Georgia USA Brookhaven National Laboratory Upton New York USA Department of Physics Drexel University Philadelphia Pennsylvania USA Physics Division Oak Ridge National Laboratory Oak Ridge Tennessee USA Department of Physics and Astronomy University of Tennessee Knoxville Tennessee USA Department of Physics Temple University Philadelphia Pennsylvania USA Department of Physics & Astronomy University of Hawaii Honolulu Hawaii USA Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo Waterloo Ontario Canada Center for Cosmology and AstroParticle Physics (CCAPP) Ohio State University Columbus Ohio 43210 USA Department of Physics Ohio State University Columbus Ohio 43210 USA

If dark matter has mass lower than around 1 GeV, it will not impart enough energy to cause detectable nuclear recoils in many direct-detection experiments. However, if dark matter is upscattered to high energy by collisions with cosmic rays, it may be detectable in both direct-detection experiments and neutrino experiments. We report the results of a dedicated search for boosted dark matter upscattered by cosmic rays, using ∼14.6 solar days of data from the PROSPECT reactor antineutrino experiment. We show that such a flux of upscattered dark matter would display characteristic diurnal sidereal modulation, and use this to set new experimental constraints on sub-GeV dark matter exhibiting large interaction cross sections.

关键词： Cosmic rays & astroparticles Dark matter Particle dark matter Dark matter detectors Neutrino detectors

Experimental observation of information flow in the anti-PT -symmetric system

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arXiv 2019年

作者： Wen, Jingwei Qin, Guoqing Zheng, Chao Wei, Shijie Kong, Xiangyu Xin, Tao Long, Guilu State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing100084 China Tsinghua National Laboratory for Information Science and Technology Beijing100084 China Collaborative Innovation Center of Quantum Matter Beijing100084 China Beijing Academy of Quantum Information Sciences Beijing100193 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518055 China

The recently theoretical and experimental researches related to PT -symmetric system have attracted unprecedented attention because of various novel features and potentials in extending canonical quantum mechanics. However, as the counterpart of PT -symmetry, there are only a few researches on the anti-PT -symmetric quantum system because of the challenges in the quantum simulation of anti-PT -symmetry in experiment. Here, we propose an algorithm for simulating the generalized anti-PT -symmetric system with quantum circuit. Utilizing the protocols, an oscillation of information flow is observed for the first time in our Nuclear Magnetic Resonance quantum simulator. We show that the information will recover from the environment completely when the anti-PT -symmetry is broken, whereas no information can be retrieved in the symmetry-unbroken phase. Our work opens the gate for the practical quantum simulation and experimental investigation of universal anti-PT -symmetric system in the quantum computer. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum computers

One-dimensional topological superconductivity at the edges of twisted bilayer graphene nanoribbons

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Physical Review B 2019年第9期100卷 094531-094531页

作者： Zhen-Hua Wang Fuming Xu Lin Li Rong Lü Bin Wang Wei-Qiang Chen Shenzhen Key Laboratory of Advanced Thin Films and Applications College of Physics and Optoelectronic Engineering Shenzhen University Shenzhen 518060 China Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China Beijing Computational Science Research Center Beijing 100193 China College of Physics and Electronic Engineering and Center for Computational Sciences Sichuan Normal University Chengdu 610068 China Department of Physics Tsinghua University Beijing 100084 China Collaborative Innovation Center of Quantum Matter Beijing 100084 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen 518055 China

Twisted bilayer graphene is one of the simplest van der Waals structures, and its inhomogeneous interlayer coupling can induce rich electronic properties. In twisted bilayer graphene nanoribbons (tBLGNRs), the interlayer coupling strengths are different for two ribbon edges due to the inhomogeneous bonding, which splits the edge states into two individuals in energy. The lower-energy state, localizing at the ribbon edge with the stronger interlayer coupling, is a good candidate to generate one-dimensional (1D) topological superconductivity in the presence of Rashba spin-orbit coupling, Zeeman field, and s-wave superconductivity. Majorana zero modes (MZMs) are found to be localized at both ends of this edge. The topological invariants of the system are explored by evaluating the Berry phase for infinite-length ribbons and Majorana polarization for quasi-1D ribbons, giving the same topological phase diagram. More importantly, by adjusting interlayer dislocation and uniaxial strain of tBLGNRs across the critical values, the lower-energy edge changes and 1D topological superconductivity can “jump” from one ribbon edge to the other one. Finally, by applying a gate voltage bias between bilayers or changing the interlayer distance, a MZM can transfer along the ribbon edge. The tBLGNRs provide an alternative platform to study 1D topological superconductivity and MZMs.

关键词： Majorana bound states Topological superconductors Graphene Tight-binding model

Tailoring magnetism in self-intercalated Cr1+δTe2 epitaxial films

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Physical Review Materials 2020年第11期4卷 114001-114001页

作者： Y. Fujisawa M. Pardo-Almanza J. Garland K. Yamagami X. Zhu X. Chen K. Araki T. Takeda M. Kobayashi Y. Takeda C. H. Hsu F. C. Chuang R. Laskowski K. H. Khoo A. Soumyanarayanan Y. Okada Quantum Materials Science Unit Okinawa Institute of Science and Technology (OIST) Okinawa 904-0495 Japan Applied Physics & Mathematics Department Northeastern University Boston Massachusetts 02115 USA Institute of Materials Research and Engineering Agency for Science Technology and Research 138634 Singapore Department of Electrical Engineering and Information Systems The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Center for Spintronics Research Network The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-8656 Japan Materials Sciences Research Center Japan Atomic Energy Agency Sayo Hyogo 679-5148 Japan Department of Physics National Sun Yat-sen University Kaohsiung 80424 Taiwan Institute of High Performance Computing Agency for Science Technology and Research 138632 Singapore Department of Physics National University of Singapore 117551 Singapore

Magnetic transition metal dichalcogenide (TMD) films have recently emerged as promising candidates in hosting novel magnetic phases relevant to next-generation spintronic devices. However, systematic control of the magnetization orientation, or anisotropy, and its thermal stability characterized by Curie temperature (TC), remains to be achieved in such films. Here we present self-intercalated epitaxial Cr1+δTe2 films as a platform for achieving systematic/smooth magnetic tailoring in TMD films. Using a molecular-beam epitaxy based technique, we have realized epitaxial Cr1+δTe2 films with smoothly tunable δ over a wide range (0.33–0.82), while maintaining NiAs-type crystal structure. With increasing δ, we found monotonic enhancement of TC from 160 to 350 K, and the rotation of magnetic anisotropy from out-of-plane to in-plane easy-axis configuration for fixed film thickness. Contributions from conventional dipolar and orbital moment terms are insufficient to explain the observed evolution of magnetic behavior with δ. Instead, ab initio calculations suggest that the emergence of antiferromagnetic interactions with δ, and its interplay with conventional ferromagnetism, may play a key role in the observed trends. This demonstration of tunable TC and magnetic anisotropy across room temperature in TMD films paves the way for engineering different magnetic phases for spintronic applications.

关键词： Magnetism

Mapping the intrinsic photocurrent streamlines through micromagnetic heterostructure devices

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arXiv 2020年

作者： Mayes, Morgan Farahmand, Farima Grossnickle, Maxwell Lohmann, Mark Aldosary, Mohammed Li, Junxue Aji, Vivek Shi, Jing Song, Justin C.W. Gabor, Nathaniel M. Department of Physics and Astronomy University of California 900 University Avenue RiversideCA92521 United States Laboratory of Quantum Materials Optoelectronics Materials Science and Engineering Building University of California Room 179 RiversideCA92521 United States School of Physical and Mathematical Sciences Division of Physics and Applied Physics Nanyang Technological University Singapore637371 Singapore Institute of High Performance Computing Agency of Science Technology and Research Singapore138632 Singapore

Like air flowing over a wing, optimizing the flow of electronic charge is essential to the operation of nanoscale devices. Unfortunately, the delicate interplay of charge, spin, and heat in complex devices has precluded detailed imaging of charge flow. Here, we report on the visualization of intrinsic charge current streamlines through yttrium iron garnet micromagnetic heterostructures. Scanning photovoltage microscopy of precisely designed devices leads to striking spatial patterns, with prominent photovoltage features emerging in corners and narrow constrictions. These patterns, which evolve continuously with rotation of an external magnetic field, enable rich spatial mapping of fluid-like flow. Taking inspiration from aerodynamic Clark Y airfoils, we engineer micromagnetic wing shaped devices, called electrofoils, which allow us to precisely contort, compress and decompress flowlines of electronic charge. Copyright © 2020, The Authors. All rights reserved.

关键词： Mapping

Thresholded quantum LIDAR: Exploiting Photon-Number-Resolving Detection

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Physical Review Letters 2019年第20期123卷 203601-203601页

作者： Lior Cohen Elisha S. Matekole Yoni Sher Daniel Istrati Hagai S. Eisenberg Jonathan P. Dowling Hearne Institute for Theoretical Physics and Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA School of Computer Science and Engineering Hebrew University of Jerusalem Jerusalem 91904 Israel Racah Institue for Physics Hebrew University of Jerusalem Jerusalem 91904 Israel NYU-ECNU Institute of Physics at NYU Shanghai 3663 Zhongshan Road North Shanghai 200062 China CAS-Alibaba Quantum Computing Laboratory CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 China National Institute of Information and Communications Technology 4-2-1 Nukui-Kitamachi Koganei Tokyo 184-8795 Japan

We present a technique that improves the signal-to-noise-ratio (SNR) of range-finding, sensing, and other light-detection applications. The technique filters out low photon numbers using photon-number-resolving detectors. This technique has no classical analog and cannot be done with classical detectors. We investigate the properties of our technique and show under what conditions the scheme surpasses the classical SNR. Finally, we simulate the operation of a rangefinder, showing improvement with a low number of signal samplings and confirming the theory with a high number of signal samplings.

关键词： Photon statistics quantum measurements quantum sensing