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Hofstadter spectrum in a semiconductor moiré lattice

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arXiv 2024年

作者： Zhao, Chen Wu, Ming Ma, Zhen Liang, Miao Lu, Ming Gao, Jin-Hua Xie, X.C. School of Physics Institute for Quantum Science and Engineering Huazhong University of Science and Technology Wuhan Hubei430074 China Beijing Academy of Quantum Information Sciences Beijing100193 China International Center for Quantum Materials School of Physics Peking University Beijing100871 China Institute for Nanoelectronic Devices and Quantum Computing Fudan University Shanghai200433 China Hefei National Laboratory Hefei230088 China

Recently, the Hofstadter spectrum of a twisted WSe2/MoSe2heterobilayer has been observed in experiment [C. R. Kometter, et al. Nat. Phys. 19, 1861 (2023)], but the origin of Hofstadter states remains unclear. Here, we present a comprehensive theoretical interpretation of the observed Hofstadter states by calculating its accurate Hofstadter spectrum. We point out that the valley Zeeman effect, a unique feature of the transition metal dichalcogenide (TMD) materials, plays a crucial role in determining the shape of the Hofstadter spectrum, due to the narrow bandwidth of the moiré bands. This is distinct from the graphene-based moiré systems. We further predict that the Hofstadter spectrum of the moiré flat band, which was not observed in experiment, can be observed in the same system with a larger twist angle 2° θ 3°. Our theory paves the way for further studies of the interplay between the Hofstadter states and correlated insulting states in such moiré lattice systems. © 2024, CC BY-SA.

关键词： Graphene

AutoQ 2.0: From Verification of quantum Circuits to Verification of quantum Programs 31th

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AutoQ 2.0: From Verification of Quantum Circuits to Verific...

31st International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2025, which was held as part of the International Joint Conferences on Theory and Practice of Software, ETAPS 2025

作者： Chen, Yu-Fang Chung, Kai-Min Hsieh, Min-Hsiu Huang, Wei-Jia Lengál, Ondřej Lin, Jyun-Ao Tsai, Wei-Lun Institute of Information Science Academia Sinica Taipei Taiwan Hon Hai Quantum Computing Research Center Taipei Taiwan Faculty of Information Technology Brno University of Technology Brno Czech Republic Innovation Frontier Institute of Research for Science and Technology & Department of Computer Science and Information Engineering National Taipei University of Technology Taipei Taiwan

ISBN: (纸本)9783031906596

We present a verifier of quantum programs called AutoQ 2.0. quantum programs extend quantum circuits (the domain of AutoQ 1.0) by classical control flow constructs, which enable users to describe advanced quantum algorithms in a formal and precise manner. The extension is highly non-trivial, as we needed to tackle both theoretical challenges (such as the treatment of measurement, the normalization problem, and lifting techniques for verification of classical programs with loops to the quantum world), and engineering issues (such as extending the input format with a support for specifying loop invariants). We have successfully used AutoQ 2.0 to verify two types of advanced quantum programs that cannot be expressed using only quantum circuits: the repeat-until-success (RUS) algorithm and the weak-measurement-based version of Grover’s search algorithm. AutoQ 2.0 can efficiently verify all our benchmarks: all RUS algorithms were verified instantly and, for the weak-measurement-based version of Grover’s search, we were able to handle the case of 100 qubits in ∼20 minutes. © The Author(s) 2025.

关键词： Qubits

One-step replica symmetry breaking in the language of tensor networks

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arXiv 2023年

作者： Pancotti, Nicola Gray, Johnnie AWS Center for Quantum Computing PasadenaCA91125 United States California Institute of Technology PasadenaCA United States Division of Chemistry and Chemical Engineering California Institute of Technology Pasadena91125 United States

We develop an exact mapping between the one-step replica symmetry breaking cavity method and tensor networks. The two schemes come with complementary mathematical and numerical toolboxes that could be leveraged to improve the respective states of the art. As an example, we construct a tensor-network representation of Survey Propagation, one of the best deterministic k-SAT solvers. The resulting algorithm outperforms any existent tensor-network solver by several orders of magnitude. We comment on the generality of these ideas, and we show how to extend them to the context of quantum tensor networks. Copyright © 2023, The Authors. All rights reserved.

关键词： Tensors

Small sets of genuinely nonlocal Greenberger-Horne-Zeilinger states in multipartite systems

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Physical Review A 2024年第2期109卷 022428-022428页

作者： Zong-Xing Xiong Yongli Zhang Mao-Sheng Li Lvzhou Li Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-Sen University Guangzhou 510006 China School of Mathematics and Systems Science Guangdong Polytechnic Normal University Guangzhou 510665 China School of Mathematics South China University of Technology Guangzhou 510641 China

A set of orthogonal multipartite quantum states are called (distinguishability-based) genuinely nonlocal if they are locally indistinguishable across any bipartition of the subsystems. In this work, we consider the problem of constructing small genuinely nonlocal sets consisting of generalized Greenberger-Horne-Zeilinger (GHZ) states in multipartite systems. For system (C2)⊗N where N is large, using the language of group theory, we show that a tiny proportion Θ(1/2N) of the states among the N-qubit GHZ basis suffice to exhibit genuine nonlocality. Similar arguments also hold for the canonical generalized GHZ bases in systems (Cd)⊗N, wherever d is even and N is large. What is more, moving to the condition that any fixed N is given, we show that d+1 genuinely nonlocal generalized GHZ states exist in (Cd)⊗N, provided the local dimension d is sufficiently large. As an additional merit, within and beyond an asymptotic sense, the latter result also indicates some evident limitations of the “trivial othogonality-preserving local measurements” (TOPLM) technique that has been utilized frequently for detecting genuine nonlocality.

关键词： Nonlocality quantum correlations in quantum information

Entanglement-Enabled Advantage for Learning a Bosonic Random Displacement Channel

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Physical Review Letters 2024年第23期133卷 230604-230604页

作者： Changhun Oh Senrui Chen Yat Wong Sisi Zhou Hsin-Yuan Huang Jens A. H. Nielsen Zheng-Hao Liu Jonas S. Neergaard-Nielsen Ulrik L. Andersen Pritzker School of Molecular Engineering The University of Chicago Chicago Illinois 60637 USA Department of Physics Korea Advanced Institute of Science and Technology Daejeon 34141 Korea Perimeter Institute for Theoretical Physics Waterloo Ontario N2L 2Y5 Canada Institute for Quantum Information and Matter California Institute of Technology Pasadena California 91125 USA Department of Physics and Astronomy and Institute for Quantum Computing University of Waterloo Ontario N2L 2Y5 Canada Center for Theoretical Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA Google Quantum AI Venice California USA Center for Macroscopic Quantum States (bigQ) Department of Physics Technical University of Denmark Building 307 Fysikvej 2800 Kgs. Lyngby Denmark

We show that quantum entanglement can provide an exponential advantage in learning properties of a bosonic continuous-variable (CV) system. The task we consider is estimating a probabilistic mixture of displacement operators acting on n bosonic modes, called a random displacement channel. We prove that if the n modes are not entangled with an ancillary quantum memory, then the channel must be sampled a number of times exponential in n in order to estimate its characteristic function to reasonable precision; this lower bound on sample complexity applies even if the channel inputs and measurements performed on channel outputs are chosen adaptively or have unrestricted energy. On the other hand, we present a simple entanglement-assisted scheme that only requires a number of samples independent of n in the large squeezing and noiseless limit. This establishes an exponential separation in sample complexity. We then analyze the effect of photon loss and show that the entanglement-assisted scheme is still significantly more efficient than any lossless entanglement-free scheme under mild experimental conditions. Our work illuminates the role of entanglement in learning CV systems and points toward experimentally feasible demonstrations of provable entanglement-enabled advantage using CV quantum platforms.

关键词： Machine learning quantum channels quantum correlations in quantum information quantum entanglement quantum information processing quantum information processing with continuous variables quantum information theory quantum metrology quantum parameter estimation quantum protocols Resource theories

Microwave-optical entanglement from pulse-pumped electro-optomechanics

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Physical Review Applied 2024年第6期22卷 064047-064047页

作者： Changchun Zhong Fangxin Li Srujan Meesala Steven Wood David Lake Oskar Painter Liang Jiang Department of Physics Xi’an Jiaotong University Xi’an Shanxi 710049 China Department of Physics University of Chicago Chicago Illinois 60637 USA Institute for Quantum Information and Matter California Institute of Technology Pasadena California 91125 USA Kavli Nanoscience Institute and Thomas J. Watson Sr. Laboratory of Applied Physics California Institute of Technology Pasadena California 91125 USA Center for Quantum Computing Amazon Web Services Pasadena California 91125 USA Pritzker School of Molecular Engineering University of Chicago Chicago Illinois 60637 USA

Entangling microwave and optical photons is one of the promising ways to realize quantum transduction through quantum teleportation. This paper investigates the entanglement of microwave-optical photon pairs generated from an electro-optomechanical system driven by a blue-detuned pulsed Gaussian pump. The photon pairs are obtained through weak parametric-down-conversion, and their temporal correlation is revealed by the second-order correlation function. We then study the discrete variable entanglement encoded in the time-bin degree of freedom, where entanglement is identified by Bell-inequality violation. Furthermore, we estimate the laser-induced heating and show that the pulse-pumped system features lower heating effects while maintaining a reasonable coincidence photon-counting rate.

关键词： quantum entanglement

Ultrafast Green Single Photon Emission from an InGaN quantum Dot-in-a-GaN Nanowire at Room Temperature

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arXiv 2023年

作者： Bhunia, Swagata Majumder, Ayan Chatterjee, Soumyadip Sarkar, Ritam Nag, Dhiman Saha, Kasturi Mahapatra, Suddhasatta Laha, Apurba Department of Physics Indian Institute of Technology Bombay Mumbai Powai400076 India Department of Electrical Engineering Indian Institute of Technology Bombay Mumbai Powai400076 India Centre of Excellence in Quantum Information Computing Science & Technology QuICST India

In recent years, there has been a growing demand for room-temperature visible single-photon emission from InGaN nanowire-quantum-dots (NWQDs) due to its potential in developing quantum computing, sensing, and communication technologies. Despite various approaches explored for growing InGaN quantum dots on top of nanowires (NWs), achieving the emission of a single photon at room temperature with sensible efficiency remains a challenge. This challenge is primarily attributed to difficulties in accomplishing the radial confinement limit and the inherent giant built-in potential of the NWQD. In this report, we have employed a novel Plasma Assisted Molecular Beam Epitaxy (PAMBE) growth approach to reduce the diameter of the QD to the excitonic Bohr radius of InGaN, thereby achieving strong lateral confinement. Additionally, we have successfully suppressed the strong built-in potential by reducing the QD diameter. Toward the end of the report, we have demonstrated single-photon emission (λ=561 nm) at room-temperature from the NWQD and measured the second-order correlation function g2 (0) as 0.11, which is notably low compared to other reported findings. Furthermore, the lifetime of carriers in the QD is determined to be 775 ps, inferring a high operational speed of the devices. Introduction: Copyright © 2023, The Authors. All rights reserved.

关键词： Nanowires

Improved distributed quantum algorithm for Simon’s problem

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arXiv 2025年

作者： Li, Hao Qiu, Daowen Qiu, D. Institute of Quantum Computing and Software School of Computer Science and Engineering Sun Yat-sen University Guangzhou510006 China The Guangdong Key Laboratory of Information Security Technology Sun Yat-sen University Guangzhou510006 China

Simon’s problem is one of the most important problems demonstrating the power of quantum computing. Recently, an interesting distributed quantum algorithm for Simon’s problem was proposed, where a key sorting operator requiring a large number of qubits was employed. In this paper, we design an improved distributed quantum algorithm for Simon’s problem without using sorting operators, and our algorithm has the advantage of reducing half number of qubits required for a single computing node. Moreover, our algorithm does not involve the classical search process. Copyright © 2025, The Authors. All rights reserved.

关键词： Qubits

Timing Jitter Remover for Optical Non-Gaussian State Preparation

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Timing Jitter Remover for Optical Non-Gaussian State Prepara...

Frontiers in Optics, FiO 2022

作者： Sonoyama, Tatsuki Takahashi, Kazuma Takasu, Sachiko Hattori, Kaori Fukuda, Daiji Asavanant, Warit Takase, Kan Fukui, Kosuke Yoshikawa, Jun-Ichi Endo, Mamoru Furusawa, Akira Department of Applied Physics School of Engineering The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo113-8656 Japan National Institute of Advanced Industrial Science and Technology Ibaraki Tsukuba305-8563 Japan AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory Ibaraki Tsukuba305-8563 Japan Optical Quantum Computing Research Team RIKEN Center for Quantum Computing 2-1 Hirosawa Saitama Wako351-0198 Japan

In this work, we remove the timing jitter of the photon-number-resolving detector which limited non-Gaussian state preparation using a continuous-wave light source, and generate a Schrödinger cat state with Wigne...

ISBN: (纸本)9781557528209

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