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arXiv 2019年

作者： Osat, Saeed Radicchi, Filippo Papadopoulos, Fragkiskos Deep Quantum Labs Skolkovo Institute of Science and Technology Moscow43026 Center for Complex Networks and Systems Research Luddy School of Informatics Computing and Engineering Indiana University BloomingtonIN47408 United States Department of Electrical Engineering Computer Engineering and Informatics Cyprus University of Technology 33 Saripolou Street Limassol3036

Multiplex networks are convenient mathematical representations for many real-world - biological, social, and technological - systems of interacting elements, where pairwise interactions among elements have different flavors. Previous studies pointed out that real-world multiplex networks display significant inter-layer correlations - degree-degree correlation, edge overlap, node similarities - able to make them robust against random and targeted failures of their individual components. Here, we show that inter-layer correlations are important also in the characterization of their k-core structure, namely the organization in shells of nodes with increasingly high degree. Understanding k-core structures is important in the study of spreading processes taking place on networks, as for example in the identification of influential spreaders and the emergence of localization phenomena. We find that, if the degree distribution of the network is heterogeneous, then a strong k-core structure is well predicted by significantly positive degree-degree correlations. However, if the network degree distribution is homogeneous, then strong k-core structure is due to positive correlations at the level of node similarities. We reach our conclusions by analyzing different real-world multiplex networks, introducing novel techniques for controlling inter-layer correlations of networks without changing their structure, and taking advantage of synthetic network models with tunable levels of inter-layer correlations. Copyright © 2019, The Authors. All rights reserved.

关键词： Network layers

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Recurrent neural networks made of magnetic tunnel junctions

arXiv

引用

arXiv 2019年

作者： Zheng, Qi Zhu, Xiaorui Mi, Yuanyuan Yuan, Zhe Xia, Ke Center for Advanced Quantum Studies Department of Physics Beijing Normal University Beijing100875 China Center for Neurointelligence Chongqing University Chongqing400044 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518005 China Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China

Artificial intelligence based on artificial neural networks, which are originally inspired by the biological architectures of human brain, has mostly been realized using software but executed on conventional von Neumann computers, where the so-called von Neumann bottleneck essentially limits the executive efficiency due to the separate computing and storage units. Therefore, a suitable hardware platform that can exploit all the advantages of brain-inspired computing is highly desirable. Based upon micromagnetic simulation of the magnetization dynamics, we demonstrate theoretically and numerically that recurrent neural networks consisting of as few as 40 magnetic tunnel junctions can generate and recognize periodic time series after they are trained with an efficient algorithm. Copyright © 2019, The Authors. All rights reserved.

关键词： Brain

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quantum Capacity of Partially Corrupted quantum Network

arXiv

引用

arXiv 2019年

作者： Hayashi, Masahito Song, Seunghoan Graduate School of Mathematics Nagoya University Nagoya464-8602 Japan Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518000 China Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 117542 Singapore

We discuss a quantum network, in which the sender has m0 outgoing channels, the receiver has m0 incoming channels, each channel is of capacity d, each intermediate node applies invertible unitary, only m1 channels are corrupted, and other non-corrupted channels are noiseless. As our result, we show that the quantum capacity is not smaller than (m0 − 2m1 + 1) log d under the following two settings. In the first case, the unitaries on intermediate nodes are arbitrary and the corruptions on the m1 channels are individual. In the second case, the unitaries on intermediate nodes are restricted to Clifford operations and the corruptions on the m1 channels are adaptive, i.e., the attacker is allowed to have a quantum memory. Further, our code in the second case realizes the noiseless communication even with the single-shot setting and is constructed dependently only on the network topology and the places of the m1 corrupted channels while this result holds regardless of the network topology and the places. Copyright © 2019, The Authors. All rights reserved.

关键词： Topology

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Pendellösung interferometry probes the neutron charge radius, lattice dynamics, and fifth forces

arXiv

引用

arXiv 2021年

作者： Heacock, Benjamin Fujiie, Takuhiro Haun, Robert W. Henins, Albert Hirota, Katsuya Hosobata, Takuya Huber, Michael G. Kitaguchi, Masaaki Pushin, Dmitry A. Shimizu, Hirohiko Takeda, Masahiro Valdillez, Robert Yamagata, Yutaka Young, Albert R. National Institute of Standards and Technology GaithersburgMD20899 United States Department of Physics North Carolina State University RaleighNC27695 United States Triangle Universities Nuclear Laboratory DurhamNC27708 United States Department of Physics Nagoya University Nagoya464-8602 Japan RIKEN Center for Advanced Photonics RIKEN Hirosawa 2-1 Saitama Wako351-0198 Japan Institute for Physical Science and Technology University of Maryland College ParkMD20742 United States Department of Physics and Engineering Physics Tulane University New OrleansLA70118 United States High Energy Accelerator Research Organization Tsukuba305-0801 Japan Kobayashi-Maskawa Institute Nagoya University Nagoya464-8602 Japan Institute for Quantum Computing University of Waterloo WaterlooONN2L3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L3G1 Canada

Structure factors describe how incident radiation is scattered from materials such as silicon and germanium and characterize the physical interaction between the material and scattered particles. We use neutron pendellösung interferometry to make precision measurements of the (220) and (400) neutron-silicon structure factors, and achieve a factor of four improvement in the (111) structure factor uncertainty. These data provide measurements of the silicon Debye-Waller factor at room temperature and the mean square neutron charge radius (rn2 ) = −0.1101 ± 0.0089 fm2. Combined with existing measurements of the Debye-Waller factor and charge radius, the measured structure factors also improve constraints on the strength of a Yukawa-modification to gravity by an order of magnitude over the 20 pm to 10 nm length scale range. © 2021, CC BY.

关键词： Interferometry

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Josephson-junction infrared single-photon detector

arXiv

引用

arXiv 2020年

作者： Walsh, Evan D. Jung, Woochan Lee, Gil-Ho Efetov, Dmitri K. Wu, Bae-Ian Huang, K.-F. Ohki, Thomas A. Taniguchi, Takashi Watanabe, Kenji Kim, Philip Englund, Dirk Fong, Kin Chung Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Department of Physics Pohang University of Science and Technology Pohang790-784 Korea Republic of Department of Physics Harvard University CambridgeMA02138 United States 08860 Spain Air Force Research Laboratory Wright-Patterson AFB OH45433 United States Raytheon BBN Technologies Quantum Engineering and Computing Group CambridgeMA02138 United States International Center for Materials Nanoarchitectonics National Institute for Materials Science Tsukuba Japan Research Center for Functional Materials National Institute for Materials Science Tsukuba Japan

Josephson junctions (JJs) are ubiquitous superconducting devices, enabling high sensitivity magnetometers and voltage amplifiers, as well as forming the basis of high performance cryogenic computer and superconducting quantum computers. While JJ performance can be degraded by quasiparticles (QPs) formed from broken Cooper pairs, this phenomenon also opens opportunities to sensitively detect electromagnetic radiation. Here we demonstrate single near-infrared photon detection by coupling photons to the localized surface plasmons of a graphene-based JJ. Using the photon-induced switching statistics of the current-biased JJ, we reveal the critical role of QPs generated by the absorbed photon in the detection mechanism. The photon-sensitive JJ will enable a high-speed, low-power optical interconnect for future JJ-based computing architectures. Copyright © 2020, The Authors. All rights reserved.

关键词： Photons

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Towards the manipulation of topological states of matter： a perspective from electron transport

引用

Science Bulletin 2018年第9期63卷 580-594页

作者： Cheng Zhang Hai-Zhou Lu Shun-Qing Shen Yong P. Chen Faxian Xi State Key Laboratory of Surface Physics and Department of Physics Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China Institute for Quantum Science and Engineering and Department of Physics South University of Science and Technology of China Shenzhen 518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Shenzhen 518055 China Department of Physics The University of Hong Kong. Hong Kong China Department of Physics and Astronomy Purdue University West Lafayette 47907 USA Birck Nanotechnology Center Purdue University West Lafayette 47907 USA School of Electrical and Computer Engineering Purdue University West Lafayette 47907 USA Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 China

The introduction of topological invariants, ranging from insulators to metals, has provided new insights into the traditional classification of electronic states in condensed matter physics. A sudden change in the topological invariant at the boundaw of a topological nontrivial system leads to the formation of exotic surface states that are dramatically different from its bulk. In recent years, significant advancements in the exploration of the physical properties of these topological systems and regarding device research related to spintronics and quantum computation have been made. Here, we review the progress of the characterization and manipulation of topological phases from the electron transport perspective and also the intriguing chiral/Majorana states that stem from them. We then discuss the future directions of research into these topological states and their potential applications.

关键词： Topological insulator Dirac semimetal Weyl semimetal quantum transport

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Second-Order Perturbation in Adaptive Perturbation Method

arXiv

引用

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

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Edge current and orbital angular momentum of chiral superfluids revisited

arXiv

引用

arXiv 2019年

作者： Nie, Wenxing Huang, Wen Yao, Hong Center for Theoretical Physics College of Physics Sichuan University Chengdu610064 Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 Institute for Advanced Study Tsinghua University Beijing100084 Center for Quantum Computing Peng Cheng Laboratory Shenzhen518005 State Key Laboratory of Low Dimensional Quantum Physics Tsinghua University Beijing100084

Cooper pairs in chiral superfluids carry quantized units of relative orbital angular momentum (OAM). Various predictions of the intrinsic OAM density or the total OAM of a chiral superfluid differ by several orders of magnitude, which constitute the so-called Angular Momentum Paradox. Following several previous studies, we substantiate the semiclassical Bogoliubov-de Gennes theory of the single-particle edge current and OAM in two-dimensional chiral superfluids in the BCS limit. The analysis provides a simple intuitive understanding for the vanishing of OAM of a non-p-wave chiral superfluid (such as d + id) confined in a rigid potential. When generalized to anisotropic chiral superconductors and three-dimensional (3D) chiral superfluids, the theory similarly returns an accurate description. We also present a detailed numerical study of the chiral phases in the BEC limit, where the OAM density is found to vanish in the bulk and arise purely from boundary effects. Copyright © 2019, The Authors. All rights reserved.

关键词： Angular momentum

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quantum invariants and the graph isomorphism problem

引用

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

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Application of a resource theory of channels to communication scenarios

arXiv

引用

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

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