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Customized quantum annealing schedules

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arXiv 2021年

作者： Khezri, Mostafa Dai, Xi Yang, Rui Albash, Tameem Lupascu, Adrian Lidar, Daniel A. Department of Electrical Engineering University of Southern California Los AngelesCA90089 United States Center for Quantum Information Science & Technology University of Southern California Los AngelesCA90089 United States Department of Physics and Astronomy University of Waterloo WaterlooON Canada Institute for Quantum Computing University of Waterloo WaterlooON Canada Department of Electrical and Computer Engineering University of New Mexico AlbuquerqueNM87131 United States Center for Quantum Information and Control CQuIC University of New Mexico AlbuquerqueNM87131 United States Department of Chemistry University of Southern California Los AngelesCA90089 United States Department of Physics University of Southern California Los AngelesCA90089 United States

In a typical quantum annealing protocol, the system starts with a transverse field Hamiltonian which is gradually turned off and replaced by a longitudinal Ising Hamiltonian. The ground state of the Ising Hamiltonian encodes the solution to the computational problem of interest, and the state overlap with this ground state gives the success probability of the annealing protocol. The form of the annealing schedule can have a significant impact on the ground state overlap at the end of the anneal, so precise control over these annealing schedules can be a powerful tool for increasing success probabilities of annealing protocols. Here we show how superconducting circuits, in particular capacitively shunted flux qubits (CSFQs), can be used to construct quantum annealing systems by providing tools for mapping circuit flux biases to Pauli coefficients. We use this mapping to find customized annealing schedules: appropriate circuit control biases that yield a desired annealing schedule, while accounting for the physical limitations of the circuitry. We then provide examples and proposals that utilize this capability to improve quantum annealing performance. Copyright © 2021, The Authors. All rights reserved.

关键词： Annealing

Leveraging randomized compiling for the QITE algorithm

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arXiv 2021年

作者： Ville, Jean-Loup Morvan, Alexis Hashim, Akel Naik, Ravi K. Lu, Marie Mitchell, Bradley Kreikebaum, John-Mark O’Brien, Kevin P. Wallman, Joel J. Hincks, Ian Emerson, Joseph Smith, Ethan Younis, Ed Iancu, Costin Santiago, David I. Siddiqi, Irfan Quantum Nanoelectronics Laboratory Dept. of Physics University of California at Berkeley BerkeleyCA94720 United States Computational Research Division Lawrence Berkeley National Lab BerkeleyCA94720 United States Materials Sciences Division Lawrence Berkeley National Lab BerkeleyCA94720 United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Inst. for Quantum Computing Dept. of Applied Mathematics University of Waterloo WaterlooONN2L 3G1 Canada Quantum Benchmark Inc. KitchenerONN2H 5G5 Canada

The success of the current generation of Noisy Intermediate-Scale quantum (NISQ) hardware shows that quantum hardware may be able to tackle complex problems even without error correction. One outstanding issue is that of coherent errors arising from the increased complexity of these devices. These errors can accumulate through a circuit, making their impact on algorithms hard to predict and mitigate. Iterative algorithms like quantum Imaginary Time Evolution are susceptible to these errors. This article presents the combination of both noise tailoring using Randomized Compiling and error mitigation with a purification. We also show that Cycle Benchmarking gives an estimate of the reliability of the purification. We apply this method to the quantum Imaginary Time Evolution of a Transverse Field Ising Model and report an energy estimation and a ground state infidelity both below 1%. Our methodology is general and can be used for other algorithms and platforms. We show how combining noise tailoring and error mitigation will push forward the performance of NISQ devices. © 2021, CC BY.

关键词： Benchmarking

Communication cost of quantum channels

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arXiv 2020年

作者： Yang, Yuxiang Chiribella, Giulio Hayashi, Masahito Institute for Theoretical Physics ETH Zurich Department of Computer Science University of Hong Kong Pokfulam Road Hong Kong Department of Computer Science University of Oxford Parks Road Oxford United Kingdom HKU Shenzhen Institute of Research and Innovation Kejizhong 2nd Road Shenzhen China Perimeter Institute For Theoretical Physics 31 Caroline Street North WaterlooONN2L 2Y5 Canada 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

In distributed computing, it is common for a server to execute a program of a remote client, consuming the minimum amount of communication. We extend such a setting to the quantum regime and consider the task of communicating quantum channels for the purpose of executing them a given number of times. We derive a general lower bound for the amount of required communication. The bound shows that the amount of required communication is positively correlated to the performance of the channels in quantum metrology. We also propose a protocol achieving the bound for a type of channels. Copyright © 2020, The Authors. All rights reserved.

关键词： quantum entanglement

quantum technologies for climate change: Preliminary assessment

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arXiv 2021年

作者： Berger, Casey Paolo, Agustin Di Forrest, Tracey Hadfield, Stuart Sawaya, Nicolas Stęchly, Michal Thibault, Karl Department of Physics Smith College NorthamptonMA01063 United States Boston University Rafik B Hariri Institute for Computing and Computational Science & Engineering BostonMA02215 United States Département de physique Institut quantique Université de Sherbrooke SherbrookeQCJ1K 2R1 Canada Transformative Quantum Technologies University of Waterloo WaterlooON Canada USRA Research Institute for Advanced Computer Science Mountain ViewCA94043 United States Intel Labs Santa ClaraCA95054 United States Zapata Computing Canada Inc. 325 Front St W TorontoONM5V 2Y1 Canada

Climate change presents an existential threat to human societies and the Earth’s ecosystems more generally. Mitigation strategies naturally require solving a wide range of challenging problems in science, engineering, and economics. In this context, rapidly developing quantum technologies in computing, sensing, and communication could become useful tools to diagnose and help mitigate the effects of climate change. However, the intersection between climate and quantum sciences remains largely unexplored. This preliminary report aims to identify potential high-impact use-cases of quantum technologies for climate change with a focus on four main areas: simulating physical systems, combinatorial optimization, sensing, and energy efficiency. We hope this report provides a useful resource towards connecting the climate and quantum science communities, and to this end we identify relevant research questions and next steps. Copyright © 2021, The Authors. All rights reserved.

关键词： Climate change

Experimental Evidence of Topological Surface States in Mg3Bi2 Films Grown by Molecular Beam Epitaxy

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Chinese Physics Letters 2019年第11期36卷 65-69页

作者： Tong Zhou Xie-Gang Zhu Mingyu Tong Yun Zhang Xue-Bing Luo Xiangnan Xie Wei Feng Qiuyun Chen Shiyong Tan Zhen-Yu Wang Tian Jiang Yuhua Tang Xin-Chun Lai Xuejun Yang State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073 Science and Technology on Surface Physics and Chemistry Laboratory Jiangyou 621908 National Innovation Institute of Defense Technology Academy of Military Sciences PLA ChinaBeijing 100010 Institute of Materials China Academy of Engineering PhysicsMianyang 621700 College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073 Academy of Military Sciences PLA China Beijing 100010 Beijing Academy of Quantum Information Sciences Beijing 100084

Nodal line semimetal(NLS) is a new quantum state hosting one-dimensional closed loops formed by the crossing of two bands. The so-called type-Ⅱ NLS means that these two crossing bands have the same sign in their slopes along the radial direction of the loop, which requires that the crossing bands are either right-tilted or left-tilted at the same time. According to the theoretical prediction, Mg3Bi2 is an ideal candidate for studying the type-Ⅱ NLS by tuning its spin-orbit coupling(SOC). High-quality Mg3 Bi2 films are grown by molecular beam epitaxy(MBE). By in-situ angle resolved photoemission spectroscopy(ARPES), a pair of surface resonance bands around theГ point are clearly seen. This shows that Mg3Bi2 films grown by MBE are Mg(1)-terminated by comparing the ARPES spectra with the first principles calculations results. Moreover, the temperature dependent weak anti-localization effect in Mg3Bi2 films is observed under magneto-transport measurements, which shows clear two-dimensional(2 D) e-e scattering characteristics by fitting with the Hikami–Larkin–Nagaoka model. Therefore, by combining with ARPES, magneto-transport measurements and the first principles calculations, this work proves that Mg3Bi2 is a semimetal with topological surface states. This paves the way for Mg3Bi2 to be used as an ideal material platform to study the exotic features of type-Ⅱ nodal line semimetals and the topological phase transition by tuning its SOC.

关键词： bands topological terminated

XYZ spectroscopy at electron-hadron facilities II: Semi-inclusive processes with pion exchange

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arXiv 2022年

作者： Winney, D. Pilloni, A. Mathieu, V. Hiller Blin, A.N. Albaladejo, M. Smith, W.A. Szczepaniak, A. Guangdong Provincial Key Laboratory of Nuclear Science Institute of Quantum Matter South China Normal University Guangzhou510006 China Guangdong-Hong Kong Joint Laboratory of Quantum Matter Southern Nuclear Science Computing Center South China Normal University Guangzhou510006 China Dipartimento di Scienze Matematiche e Informatiche Scienze Fisiche e Scienze della Terra Università degli Studi di Messina MessinaI-98122 Italy INFN Sezione di Catania CataniaI-95123 Italy Departament de Física Quàntica i Astrofísica Institut de Ciències del Cosmos Universitat de Barcelona E-08028 Spain Institute for Theoretical Physics Regensburg University RegensburgD-93040 Germany Institute for Theoretical Physics Tübingen University Auf der Morgenstelle 14 Tübingen72076 Germany Centro Mixto CSIC-Universidad de Valencia ValenciaE-46071 Spain Center for Exploration of Energy and Matter Indiana University BloomingtonIN47403 United States Department of Physics Indiana University BloomingtonIN47405 United States Theory Center Thomas Jefferson National Accelerator Facility Newport NewsVA23606 United States

Semi-inclusive processes are very promising to investigate XYZ hadrons at the next generation of electron-hadron facilities, because they generally boast higher cross sections. We extend our formalism of exclusive photoproduction to semi-inclusive final states. The inclusive production cross sections for charged axial-vector Z states from pion exchange are predicted. We isolate the contribution of ∆ resonances at small missing mass. Production near threshold is shown to be enhanced roughly by a factor of two compared to the exclusive reaction. We benchmark the model with data of semi-inclusive b±1 production. Copyright © 2022, The Authors. All rights reserved.

关键词： Hadrons

Demonstration of long-range correlations via susceptibility measurements in a one-dimensional superconducting Josephson spin chain

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arXiv 2021年

作者： Tennant, Daniel M. Dai, Xi Martinez, Antonio J. Trappen, Robbyn Melanson, Denis Yurtalan, M.A. Tang, Yongchao Bedkihal, Salil Yang, Rui Novikov, Sergei Grover, Jeffery A. Disseler, Steven M. Basham, James I. Das, Rabindra Kim, David K. Melville, Alexander J. Niedzielski, Bethany M. Weber, Steven J. Yoder, Jonilyn L. Kerman, Andrew J. Mozgunov, Evgeny Lidar, Daniel A. Lupascu, Adrian Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Northrop Grumman Corporation LinthicumMD21090 United States MIT Lincoln Laboratory LexingtonMA02421 United States Center for Quantum Information Science & Technology University of Southern California Los AngelesCA90089 United States Departments of Electrical & Computer Engineering Chemistry and Physics Waterloo Institute for Nanotechnology University of Waterloo WaterlooONN2L 3G1 Canada

Spin chains have long been considered an effective medium for long-range interactions, entanglement generation, and quantum state transfer. In this work, we explore the properties of a spin chain implemented with superconducting flux circuits, designed to act as a connectivity medium between two superconducting qubits. The susceptibility of the chain is probed and shown to support long-range, cross chain correlations. In addition, interactions between the two end qubits, mediated by the coupler chain, are demonstrated. This work has direct applicability in near term quantum annealing processors as a means of generating long-range, coherent coupling between qubits. © 2021, CC BY.

关键词： Spin dynamics

Gate-Tunable Multi-Band van der Waals Photodetector and Polarization Sensor

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arXiv 2024年

作者： Shen, Daozhi Yang, HeeBong Patel, Tarun Rhodes, Daniel A. Timusk, Thomas Zhou, Y. Norman Kim, Na Young Tsen, Adam W. School of Mechanical Engineering Shanghai Jiao Tong University Shanghai200240 China Institute for Quantum Computing University of Waterloo WaterlooONN2L 3G1 Canada Department of Chemistry University of Waterloo WaterlooONN2L 3G1 Canada Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada Department of Materials Science and Engineering University of Wisconsin-Madison WI United States Department of Physics and Astronomy McMaster University HamiltonONL8S 4M1 Canada Centre for Advanced Materials Joining Department of Mechanical and Mechatronics Engineering University of Waterloo WaterlooONN2L 3G1 Canada Waterloo Institute for Nanotechnology University of Waterloo WaterlooONN2L 3G1 Canada

A single photodetector with tunable detection wavelengths and polarization sensitivity can potentially be harnessed for diverse optical applications ranging from imaging and sensing to telecommunications. Such a device will require the combination of multiple material systems with different structures, bandgaps, and photoelectrical responses, which is extremely difficult to engineer using traditional epitaxial films. Here, we develop a multi-functional and high-performance photosensor using all van der Waals materials. The device features a gate-tunable spectral response that is switchable between near-infrared/visible and short-/mid-wave infrared, as well as broadband operation, at room temperature. The linear polarization sensitivity in the telecommunications O-band can also be directly modulated between horizontal, vertical, and nonpolarizing modes. These effects originate from the balance of photocurrent generation in two of the active layers that can be manipulated by an electric field. The photodetector features high detectivity (>109 cmHz1/2W-1) together with fast operation speed (~ 1 MHz) and can be further exploited for dual visible and infrared imaging. Copyright © 2024, The Authors. All rights reserved.

关键词： Photodetectors

Van der Waals heterostructure polaritons with moiré -induced nonlinearity

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arXiv 2021年

作者： Zhang, Long Wu, Fengcheng Hou, Shaocong Zhang, Zhe Chou, Yu-Hsun Watanabe, Kenji Taniguchi, Takashi Forrest, Stephen R. Deng, Hui Physics Department University of Michigan 450 Church Street Ann ArborMI48109-2122 United States Department of Physics Xiamen University Fujian Xiamen361005 China Condensed Matter Theory Center Joint Quantum Institute Department of Physics University of Maryland College ParkMD20742 United States Department of Electrical Engineering and Computer Science University of Michigan 450 Church Street Ann ArborMI48109-1040 United States Department of Photonics National Cheng Kung University No. 1 University Road East District Tainan City70101 Taiwan Research Center for Functional Materials National Institute for Materials Science Tsukuba Japan International Center for Materials Nanoarchitectonics National Institute for Materials Science Tsukuba Japan

Controlling matter-light interactions with cavities is of fundamental importance in modern science and technology [1]. It is exemplified in the strong-coupling regime, where matter-light hybrid modes form, with properties controllable via the photon component on the optical-wavelength scale [2, 3]. In contrast, matter excitations on the nanometer scale are harder to access. In two-dimensional van der Waals heterostructures, a tunable moiré lattice potential for electronic excitations may form [4], enabling correlated electron gases in lattice potentials [5–9]. Excitons confined in moiré lattices [10, 11] have also been reported, but cooperative effects have been elusive and interactions with light have remained perturbative [12–15]. Here, integrating MoSe2 -WS2 heterobilayers in a microcavity, we establish cooperative coupling between moiré -lattice excitons and microcavity photons up to liquid-nitrogen temperature, thereby integrating into one platform versatile control over both matter and light. The density dependence of the moiré polaritons reveals strong nonlinearity due to exciton blockade, suppressed exciton energy shift, and suppressed excitation-induced dephasing, all of which are consistent with the quantum-confined nature of the moiré excitons. Such a moiré polariton system combines strong nonlinearity and microscopic-scale tuning of matter excitations with the power of cavity engineering and long range coherence of light, providing a new platform for collective phenomena from tunable arrays of quantum emitters. © 2021, CC0.

关键词： Photons