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Spatial anisotropy of the Kondo screening cloud in a type-II Weyl semimetal

Physical Review B 2019年第23期99卷 235108-235108页

作者： Lu-Ji Wang Xing-Tai Hu Lin Li Dong-Hui Xu Jin-Hua Sun Wei-Qiang Chen Department of Physics Ningbo University Ningbo 315211 China College of Physics and Electronic Engineering and Center for Computational Sciences Sichuan Normal University Chengdu 610068 China Department of Physics Hubei University Wuhan 430062 China Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen 518055 China

We theoretically study the Kondo screening of a spin-1/2 magnetic impurity in the bulk of a type-II Weyl semimetal (WSM) by use of the variational wave-function method. We consider a type-II WSM model with two Weyl nodes located on the kz axis, and the tilting of the Weyl cones are along the kx direction. Due to coexisting electron and hole pockets, the density of states at the Fermi energy becomes finite, leading to a significant enhancement of the Kondo effect. Consequently, the magnetic impurity and the conduction electrons always form a bound state; this behavior is distinct from that in type-I WSMs, where the bound state is only formed when the hybridization exceeds a critical value. Meanwhile, the spin-orbit coupling and unique geometry of the Fermi surface lead to a strongly anisotropic Kondo screening cloud in coordinate space. The tilting terms break the rotational symmetry of the type-II WSM about the kz axis, but the system remains invariant under a combined transformation TRy(π), where T is the time-reversal operation and Ry(π) is the rotation about the y axis by π. Largely modified diagonal and off-diagonal components of the spin-spin correlation function on three principal planes reflect this change in band symmetry. Most saliently, on the x−z plane, tilting terms trigger the emergence of nonzero off-diagonal spin-spin correlation function Jyz(r) and Jxy(r), while in a type-I WSM they vanish on the x−z plane.

关键词： Kondo effect Weyl semimetal Anderson impurity model Variational approach

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Physics Opportunities with PROSPECT-II

arXiv

引用

arXiv 2022年

作者： Andriamirado, M. Balantekin, A.B. Bass, C.D. Bergeron, D.E. Bernard, E.P. Bowden, N.S. Bryan, C.D. Carr, R. Classen, T. Conant, A.J. Deichert, G. Delgado, A. Diwan, M.V. Dolinski, M.J. Erickson, A. Foust, B.T. Gaison, J.K. Galindo-Uribari, A. Gilbert, C.E. Gokhale, S. Grant, C. Hans, S. Hansell, A.B. Heeger, K.M. Heffron, B. Jaffe, D.E. Jayakumar, S. Ji, X. Jones, D.C. Koblanski, J. Kunkle, P. Kyzylova, O. Lane, C.E. Langford, T.J. LaRosa, J. Littlejohn, B.R. Lu, X. Maricic, J. Mendenhall, M.P. Meyer, A.M. Milincic, R. Mueller, P.E. Mumm, H.P. Napolitano, J. Neilson, R. Nikkel, J.A. Nour, S. Palomino, J.L. Pushin, D.A. Qian, X. Roca, C. Rosero, R. Searles, M. Surukuchi, Pranava Teja Sutanto, F. Tyra, M.A. Varner, R.L. Venegas-Vargas, D. Weatherly, P.B. Wilhelmi, J. Woolverton, A. Yeh, M. Zhang, C. Zhang, X. Department of Physics Boston University BostonMA United States Brookhaven National Laboratory UptonNY United States Department of Physics Drexel University PhiladelphiaPA United States George W.Woodruff School of Mechanical Engineering Georgia Institute of Technology AtlantaGA United States Department of Physics and Astronomy University of Hawaii HonoluluHI United States Department of Physics Illinois Institute of Technology ChicagoIL United States Nuclear and Chemical Sciences Division Lawrence Livermore National Laboratory LivermoreCA United States Department of Physics Le Moyne College SyracuseNY United States National Institute of Standards and Technology GaithersburgMD United States High Flux Isotope Reactor Oak Ridge National Laboratory Oak RidgeTN United States Physics Division Oak Ridge National Laboratory Oak RidgeTN United States Department of Physics Susquehanna University SelinsgrovePA United States Department of Physics Temple University PhiladelphiaPA United States Department of Physics and Astronomy University of Tennessee KnoxvilleTN United States Department of Physics United States Naval Academy AnnapolisMD United States Institute for Quantum Computing Department of Physics University of Waterloo WaterlooON Canada Department of Physics University of Wisconsin MadisonWI United States Wright Laboratory Department of Physics Yale University New HavenCT United States

Nuclear reactors provide the highest intensity source of pure electron-type neutrinos available on earth. Reactor neutrino experiments have played a central role in developing our current understanding of the three neutrino paradigm and in establishing the current era of precision neutrino physics. Precision measurements of the flavor-pure antineutrino flux from reactors are one way to search for new physics by probing both the physics of neutrino oscillations and the production mechanism of rector antineutrinos. In the years to come reactor neutrino experiments will continue to play an important role in resolving the global neutrino picture. Unique features of reactor neutrinos mean that these experiments can continue to play a leading role in resolving the global neutrino picture. The PROSPECT experiment has substantially addressed the original 'Reactor Antineutrino Anomaly' by performing a high-resolution spectrum measurement from an enriched compact reactor core and a reactor model-independent sterile neutrino oscillation search based on the unique spectral distortions the existence of eV2-scale sterile neutrinos would impart. But as the field has evolved, the current short-baseline (SBL) landscape supports many complex phenomenological interpretations, establishing a need for complementary experimental approaches to resolve the situation. While the global suite of SBL reactor experiments, including PROSPECT, have probed much of the sterile neutrino parameter space, there remains a large region above 1 eV2 that remains unaddressed. Recent results from BEST confirm the Gallium Anomaly, increasing its significance to nearly 5σ, with sterile neutrinos providing a possible explanation of this anomaly. Separately, the MicroBooNE exclusion of electron-like signatures causing the MiniBooNE low-energy excess does not eliminate the possibility of sterile neutrinos as an explanation. In fact, MicroBooNE potentially indicates an oscillation-based deficit in the electron ne

关键词： Neutrons

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Detecting scrambling via statistical correlations between randomized measurements on an NMR quantum simulator

arXiv

引用

arXiv 2019年

作者： Nie, Xinfang Zhang, Ze Zhao, Xiuzhu Xin, Tao Lu, Dawei Li, Jun Shenzhen Institute for Quantum Science and Engineering Department of Physics Southern University of Science and Technology Shenzhen518055 China CAS Key Laboratory of Microscale Magnetic Resonance Department of Modern Physics University of Science and Technology of China Hefei230026 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen518055 China

Out-of-time-order correlator (OTOC), been suggested as a measure of quantum information scrambling in quantum many-body systems, has received enormous attention recently. The experimental measurement of OTOC is quite challenging. The existing theoretical protocols consist in implementing time-reversal operations or using ancillary quantum systems, therefore only a few experiments have been reported. Recently, a new protocol to detect OTOC using statistical correlations between randomized measurements was put forward. In this work, we detect the OTOCs of a kicked-Ising model using this new measurement method on a 4-qubit nuclear magnetic resonance quantum simulator. In experiment, we use random Hamiltonian evolutions to generate the random operations that are required by the randomized OTOC detection protocol. Our experimental results are in good agreement with the theoretical predictions, thus confirming the feasibility of the protocols. Therefore, our work represents a step in exploring realistic quantum chaotic dynamics in complicated quantum systems. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum optics

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Driving-induced resonance narrowing in a strongly coupled cavity-qubit system

arXiv

引用

arXiv 2020年

作者： Buks, Eyal Brookes, Paul Ginossar, Eran Deng, Chunqing Orgiazzi, Jean-Luc F.X. Otto, Martin Lupascu, Adrian Andrew and Erna Viterbi Department of Electrical Engineering Technion Haifa32000 Israel Department of Physics and Astronomy University College London Gower Street LondonWC1E 6BT United Kingdom Advanced Technology Institute Department of Physics University of Surrey GuildfordGU2 7XH United Kingdom Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Alibaba Quantum Laboratory Alibaba Group HangzhouZhejiang311121 China

We study a system consisting of a superconducting flux qubit strongly coupled to a microwave cavity. Externally applied qubit driving is employed in order to manipulate the spectrum of dressed states. We observe resonance narrowing in the region where the splitting between the two dressed fundamental resonances is tuned to zero. The narrowing in this region of overlapping resonances can be exploited for long-time storage of quantum states. In addition, we measure the response to strong cavity mode driving, and find a qualitative deviation between the experimental results and the predictions of a semiclassical model. On the other hand, good agreement is obtained using theoretical predictions obtained by numerically integrating the master equation governing the system’s dynamics. The observed response demonstrates a process of a coherent cancellation of two meta-stable dressed states. Copyright © 2020, The Authors. All rights reserved.

关键词： Resonance

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Structural Monoclinicity and its coupling to layered magnetism in few-layer CrI3

arXiv

引用

arXiv 2021年

作者： Guo, Xiaoyu Jin, Wencan Ye, Zhipeng Ye, Gaihua Xie, Hongchao Yang, Bowen Kim, Hyun Ho Yan, Shaohua Fu, Yang Tian, Shangjie Lei, Hechang Tsen, Adam W. Sun, Kai Yan, Jia-An He, Rui Zhao, Liuyan Department of Physics University of Michigan 450 Church Street Ann ArborMI48109 United States Department of Physics Auburn University 380 Duncan Drive AuburnAL36849 United States Department of Electrical and Computer Engineering Texas Tech University 910 Boston Ave LubbockTX79409 United States Institute for Quantum Computing Department of Physics and Astronomy Department of Chemistry University of Waterloo ONN2L 3G1 Canada School of Materials Science and Engineering Kumoh National Institute of Technology Gumi39177 Korea Republic of Department of Physics Beijing Key Laboratory of Opto-electronic Functional Materials & Micro-nano Devices Renmin University of China Beijing100872 China Department of Physics Astronomy & Geosciences Towson University TowsonMD21252 United States

Using polarization-resolved Raman spectroscopy, we investigate layer number, temperature, and magnetic field dependence of Raman spectra in one- to four-layer CrI3. Layer-number-dependent Raman spectra show that in the paramagnetic phase a doubly degenerated Eg mode of monolayer CrI3 splits into one Ag and one Bg mode in N-layer (N > 1) CrI3 due to the monoclinic stacking. Their energy separation increases in thicker samples until an eventual saturation. Temperature-dependent measurements further show that the split modes tend to merge upon cooling but remain separated until 10 K, indicating a failed attempt of the monoclinic-to-rhombohedral structural phase transition that is present in the bulk crystal. Magnetic-field-dependent measurements reveal an additional monoclinic distortion across the magnetic-field-induced layered antiferromagnetism-to-ferromagnetism phase transition. We propose a structural change that consists of both a lateral sliding toward the rhombohedral stacking and a decrease in the interlayer distance to explain our experimental observations. Copyright © 2021, The Authors. All rights reserved.

关键词： Chromium compounds

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General framework for verifying pure quantum states in the adversarial scenario

引用

Physical Review A 2019年第6期100卷 062335-062335页

作者： Huangjun Zhu Masahito Hayashi Department of Physics and Center for Field Theory and Particle Physics Fudan University Shanghai 200433 China State Key Laboratory of Surface Physics Fudan University Shanghai 200433 China Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China Graduate School of Mathematics Nagoya University Nagoya 464-8602 Japan Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Center for Quantum Computing Peng Cheng Laboratory Shenzhen 518000 China Centre for Quantum Technologies National University of Singapore 3 Science Drive 2 117542 Singapore

Bipartite and multipartite entangled states are of central interest in quantum information processing and foundational studies. Efficient verification of these states, especially in the adversarial scenario, is a key to various applications, including quantum computation, quantum simulation, and quantum networks. However, little is known about this topic in the adversarial scenario. Here we initiate a systematic study of pure-state verification in the adversarial scenario. In particular, we introduce a general method for determining the minimal number of tests required by a given strategy to achieve a given precision. In the case of homogeneous strategies, we can even derive an analytical formula. Furthermore, we propose a general recipe to verifying pure quantum states in the adversarial scenario by virtue of protocols for the nonadversarial scenario. Thanks to this recipe, the resource cost for verifying an arbitrary pure state in the adversarial scenario is comparable to the counterpart for the nonadversarial scenario, and the overhead is at most three times for high-precision verification. Our recipe can readily be applied to efficiently verify bipartite pure states, stabilizer states, hypergraph states, weighted graph states, and Dicke states in the adversarial scenario, even if only local projective measurements are accessible. This paper is an extended version of the companion paper Zhu and Hayashi, Phys. Rev. Lett. 123, 260504 (2019).

关键词： quantum entanglement quantum tomography

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High-Performance Mid-IR to Deep-UV van der Waals Photodetectors Capable of Local Spectroscopy at Room Temperature

arXiv

引用

arXiv 2022年

作者： Shen, Daozhi Yang, HeeBong Spudat, Christian Patel, Tarun Zhong, Shazhou Chen, Fangchu Yan, Jian Luo, Xuan Cheng, Meixin Sciaini, Germán Sun, Yuping Rhodes, Daniel A. Timusk, Thomas Zhou, Y. Norman Kim, Na Young Tsen, Adam W. Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Chemistry University of Waterloo WaterlooONN2L 3G1 Canada Centre for Advanced Materials Joining Department of Mechanical and Mechatronics Engineering University of Waterloo WaterlooONN2L 3G1 Canada Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada Institute of Electrodynamics Microwave and Circuit Engineering TU Wien Gusshausstrasse 25/354 Vienna1040 Austria Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Key Laboratory of Materials Physics Institute of Solid State Physics HFIPS Chinese Academy of Sciences Hefei230031 China University of Science and Technology of China Hefei230026 China Waterloo Institute for Nanotechnology University of Waterloo WaterlooONN2L 3G1 Canada Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory HFIPS Chinese Academy of Sciences Hefei230031 China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China Department of Materials Science and Engineering University of Wisconsin MadisonWI United States Department of Physics and Astronomy McMaster University HamiltonONL8S 4M1 Canada

The ability to perform broadband optical spectroscopy with sub-diffraction-limit resolution is highly sought-after for a wide range of critical applications. However, sophisticated tip-enhanced techniques are currently required to achieve this goal. We bypass this challenge by demonstrating an extremely broadband photodetector based on a two-dimensional (2D) van der Waals heterostructure that is sensitive to light across over a decade in energy from the mid-infrared (MIR) to deep-ultraviolet (DUV) at room temperature. The devices feature high detectivity (> 109 cm Hz1/2 W-1) together with high bandwidth (2.1 MHz). The active area can be further miniaturized to submicron dimensions, far below the diffraction limit for the longest detectable wavelength of 4.1 µm, enabling such devices for facile measurements of local optical properties on atomic-layer-thickness samples placed in close proximity. This work can lead to the development of low-cost and high-throughput photosensors for hyperspectral imaging at the nanoscale. © 2022, CC BY.

关键词： Van der Waals forces

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Efficient Verification of Pure quantum States in the Adversarial Scenario

引用

Physical Review Letters 2019年第26期123卷 260504-260504页

Efficient verification of pure quantum states in the adversarial scenario is crucial to many applications in quantum information processing, such as blind measurement-based quantum computation and quantum networks. However, little is known about this topic so far. Here, we establish a general framework for verifying pure quantum states in the adversarial scenario and clarify the resource cost. Moreover, we propose a simple and general recipe to constructing efficient verification protocols for the adversarial scenario from protocols for the nonadversarial scenario. With this recipe, arbitrary pure states can be verified in the adversarial scenario with almost the same efficiency as in the nonadversarial scenario. Many important quantum states can be verified in the adversarial scenario using local projective measurements with unprecedented high efficiencies.

关键词： quantum benchmarking quantum entanglement quantum tomography

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Two-Way Physical Layer Security Protocol for Gaussian Channels

arXiv

引用

arXiv 2019年

作者： Hayashi, Masahito Vázquez-Castro, Ángeles Graduate School of Mathematics Nagoya University Nagoya Japan Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen China Center for Quantum Computing Peng Cheng Laboratory Shenzhen China Centre for Quantum Technologies National University of Singapore Singapore Singapore Autonomous University of Barcelona Barcelona Spain

—In this paper we propose a two-way protocol of physical layer security using the method of privacy amplification against eavesdroppers. First we justify our proposed protocol by analyzing the physical layer security provided by the classic wiretap channel model (i.e. one-way protocol). In the Gaussian channels, the classic one-way protocol requires Eve’s channel to be degraded w.r.t. Bob’s channel. However, this channel degradation condition depends on Eve’s location and whether Eve’s receiving antenna is more powerful than Bob’s. To overcome this limitation, we introduce a two-way protocol inspired in IEEE TIT (1993) that eliminates the channel degradation condition. In the proposed two-way protocol, on a first phase, via Gaussian channel, Bob sends randomness to Alice, which is partially leaked to Eve. Then, on a second phase, Alice transmits information to Bob over a public noiseless channel. We derive the secrecy capacity of the two-way protocol when the channel to Eve is also Gaussian. We show that the capacity of the two-way protocol is always positive. We present numerical values of the capacities illustrating the gains obtained by our proposed protocol. We apply our result to simple yet realistic models of satellite communication channels. Copyright © 2019, The Authors. All rights reserved.

关键词： Receiving antennas

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Improved entanglement detection with subspace witnesses

arXiv

引用

arXiv 2019年

作者： Sun, Won Kyu Calvin Cooper, Alexandre Cappellaro, Paola Research Lab of Electronics Department of Nuclear Science and Engineering Massachusetts Institute of Technology CambridgeMA02139 United States Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada

Entanglement, while being critical in many quantum applications, is difficult to characterize experimentally. While entanglement witnesses based on the fidelity to the target entangled state are efficient detectors of entanglement, they in general underestimate the amount of entanglement due to local unitary errors during state preparation and measurement (SPAM). Therefore, to detect entanglement more robustly in the presence of such control errors, we introduce a ‘subspace’ witness that detects a broader class of entangled states with strictly larger violation than the conventional state-fidelity witness at the cost of additional measurements while remaining more efficient with respect to state tomography. We experimentally demonstrate the advantages of the subspace witness by generating and detecting entanglement with a hybrid, two-qubit system composed of electronic spins in diamond. We further extend the notion of subspace witness to specific genuine multipartite entangled (GME) states detected by the state witness, such as GHZ, W, and Dicke states, and motivate the choice of the metric based on quantum information tasks, such as entanglement-enhanced sensing. In addition, as the subspace witness identifies the many-body coherences of the target entangled state, it facilitates (beyond detection) lower bound quantification of entanglement via generalized concurrences. We expect the straightforward and efficient implementation of subspace witnesses would be beneficial in detecting specific GME states in noisy, intermediate-scale quantum processors with a hundred qubits. Copyright © 2019, The Authors. All rights reserved.

关键词： quantum optics

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