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Phase diagram of a distorted kagome antiferromagnet and application to Y-kapellasite

npj Computational Materials 2022年第1期8卷 79-88页

作者： Max Hering Francesco Ferrari Aleksandar Razpopov Igor I.Mazin Roser Valentí Harald O.Jeschke Johannes Reuther Helmholtz-Zentrum Berlin für Materialien und Energie Hahn-Meitner Platz 114109BerlinGermany Dahlem Center for Complex Quantum Systems and Fachbereich Physik Freie Universität Berlin14195BerlinGermany Institute for Theoretical Physics Goethe University FrankfurtMax-von-Laue-Straße 160438Frankfurt am MainGermany Department of Physics and Astronomy and Quantum Science and Engineering CenterGeorge Mason UniversityFairfaxVA22030USA Research Institute for Interdisciplinary Science Okayama UniversityOkayama700-8530Japan

We investigate the magnetism of a previously unexplored distorted spin-1/2 kagome model consisting of three symmetry-inequivalent nearest-neighbor antiferromagnetic Heisenberg couplings J_(■),J,and J′,and uncover a rich ground state phase diagram even at the classical *** analytical arguments and numerical techniques we identify a collinear Q^(→)=0 magnetic phase,two unusual non-collinear coplanar Q^(→)=(1/3,1/3)phases and a classical spin liquid phase with a degenerate manifold of non-coplanar ground states,resembling the jammed spin liquid phase found in the context of a bond-disordered kagome *** further show with density functional theory calculations that the recently synthesized Y-kapellasite Y_(3)Cu_(9)(OH)_(19)C_(l8) is a realization of this model and predict its ground state to lie in the region of Q^(→)=(1/3,1/3)order,which remains stable even after the inclusion of quantum fluctuation effects within variational Monte Carlo and pseudofermion functional renormalization *** presented model opens a new direction in the study of kagome antiferromagnets.

关键词： group distorted diagram

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Compressive quantum waveform estimation

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Physical Review A 2025年第2期111卷 022625-022625页

作者： Alex Tritt Joshua Morris Christopher C. Bounds Hamish A. M. Taylor James Saunderson L. D. Turner School of Physics and Astronomy Monash University Victoria 3800 Australia Present address: Vienna Center for Quantum Science and Technology Faculty of Physics University of Vienna 1010 Vienna Austria. Present address: 5 Physikalisches Institut Center for Integrated Quantum Science and Technology Universität Stuttgart Pfaffenwaldring 57 70569 Stuttgart Germany. Department of Electrical and Computer Systems Engineering Monash University Victoria 3800 Australia

quantum waveform estimation, in which quantum sensors sample entire time series, promises to revolutionize the sensing of weak and stochastic signals, such as the biomagnetic impulses emitted by firing neurons. For long duration waveforms with rapid transients, regular quantum sampling becomes prohibitively resource intensive as it demands many measurements with distinct control and readout. In this paper, we demonstrate how careful choice of quantum measurements, along with the modern mathematics of compressive sensing, achieves quantum waveform estimation of sparse signals in a number of measurements far below the Nyquist requirement. We sense synthesized neural-like magnetic waveforms with radio-frequency-dressed ultracold atoms, retrieving successful waveform estimates with as few measurements as compressive theoretical bounds guarantee.

关键词： Waveform analysis

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Andreev probing of a Cooper-pair flying qubit

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Physical Review B 2025年第16期111卷 165403-165403页

作者： S. Park L. Y. Gorelik S. I. Kulinich H. C. Park C. Kim R. I. Shekhter Center for Theoretical Physics of Complex Systems Institute for Basic Science (IBS) Daejeon 34126 Republic of Korea Department of Physics Chalmers University of Technology SE-412 96 Göteborg Sweden B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Prospekt Nauky Kharkiv 61103 Ukraine Department of Physics Pukyong National University Busan 48513 Republic of Korea Center for Quantum Technology Korea Institute of Science and Technology Seoul 02792 Republic of Korea Department of Physics University of Gothenburg SE-412 96 Göteborg Sweden

We propose a superconducting nanomechanical device that can actuate and probe an oscillating flying qubit facilitating quantum information transfer over a distance. The flying qubit is formed by a movable Cooper-pair box (CPB) consisting of a superconducting dot and a bulk superconductor, which are entangled by lifting the Coulomb blockade of Cooper-pair tunneling electrostatically. We show that flying qubit states formed on a movable CPB can be observed in electron transport to a normal electrode via Andreev reflections. The charge transfer due to periodic mechanical motion of CPB leads to the occurrence of a nonzero current at zero bias voltage, and its coherence can be identified through the oscillatory current dependence of the current on a gate voltage. The proposed device provides a building block for dissipationless quantum information circuits.

关键词： Electron transport properties

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Critical behavior of the quantum Stirling heat engine

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Physical Review A 2024年第2期109卷 022208-022208页

作者： Yuan-Sheng Wang Man-Hong Yung Dazhi Xu Maoxin Liu Xiaosong Chen School of Systems Science Beijing Normal University Beijing 100875 China Lanzhou Center for Theoretic Physics Lanzhou University Lanzhou Gansu 730000 China Department of Physics Southern University of Science and Technology Shenzhen 518055 China Shenzhen Institute for Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Guangdong Provincial Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and Technology Shenzhen 518055 China Center for Quantum Technology Research and Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China

We investigate the performance of a Stirling cycle with a working substance (WS) modeled as the quantum Rabi model (QRM), exploring the impact of criticality on its efficiency. Our findings indicate that the criticality of the QRM has a positive effect on improving the efficiency of the Stirling cycle when the WS parameters are in the normal phase. Furthermore, we observe that the Carnot efficiency is asymptotically achievable as the WS parameter approaches the critical point, even when both temperatures of the cold and hot reservoirs are finite. Additionally, we derive the critical behavior for the efficiency of the Stirling cycle, demonstrating how the efficiency asymptotically approaches the Carnot efficiency as the WS parameter approaches the critical point. Our work deepens the understanding of the impact of criticality on the performance of a Stirling heat engine.

关键词： Critical phenomena quantum phase transitions quantum thermodynamics

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Levitated Optomechanics with Meta-Atoms

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Physical Review Letters 2023年第23期130卷 233601-233601页

作者： Sergei Lepeshov Nadine Meyer Patrick Maurer Oriol Romero-Isart Romain Quidant School of Physics and Engineering ITMO University Saint Petersburg Russia Nanophotonic Systems Laboratory Department of Mechanical and Process Engineering ETH Zurich 8092 Zurich Switzerland Quantum Center ETH Zurich 8083 Zurich Switzerland Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences A-6020 Innsbruck Austria Institute for Theoretical Physics University of Innsbruck A-6020 Innsbruck Austria

We propose to introduce additional control in levitated optomechanics by trapping a meta-atom, i.e., a subwavelength and high-permittivity dielectric particle supporting Mie resonances. In particular, we theoretically demonstrate that optical levitation and center-of-mass ground-state cooling of silicon nanoparticles in vacuum is not only experimentally feasible but it offers enhanced performance over widely used silica particles in terms of trap frequency, trap depth, and optomechanical coupling rates. Moreover, we show that, by adjusting the detuning of the trapping laser with respect to the particle’s resonance, the sign of the polarizability becomes negative, enabling levitation in the minimum of laser intensity, e.g., at the nodes of a standing wave. The latter opens the door to trapping nanoparticles in the optical near-field combining red and blue-detuned frequencies, in analogy to two-level atoms, which is of interest for generating strong coupling to photonic nanostructures and short-distance force sensing.

关键词： Light-matter interaction Metamaterials Optomechanics Micromechanical & nanomechanical oscillators Polarizability Optical lattices & traps

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Layer Hall counterflow as a model probe of magic-angle twisted bilayer graphene

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Physical Review B 2024年第15期109卷 155114-155114页

作者： Jihang Zhu Dawei Zhai Cong Xiao Wang Yao Condensed Matter Theory Center and Joint Quantum Institute Department of Physics University of Maryland College Park Maryland 20742 USA Max Planck Institute for the Physics of Complex Systems 01187 Dresden Germany New Cornerstone Science Laboratory Department of Physics the University of Hong Kong Hong Kong China HKU-UCAS Joint Institute of Theoretical and Computational Physics at Hong Kong Hong Kong China Institute of Applied Physics and Materials Engineering University of Macau Taipa Macau SAR China

The recent constructions of flat moiré minibands in specifically twisted multilayer graphene and twisted transition metal dichalcogenides (TMDs) have facilitated the observation of strong correlations with convenient tunability. These correlations in flat bands result in band dispersion heavily influenced by carrier densities, leading to filling-dependent quasiparticle band renormalizations. Particularly, in magic-angle twisted bilayer graphene (MATBG), the band structure—including the quasiparticle energy and wave function—is crucial in understanding the correlated properties. Previous theoretical studies have demonstrated the presence of a time-reversal-even charge Hall counterflow in response to a direct current (DC) electric field in twisted bilayers as chiral structures. In this study, we show that such layer Hall counterflow can serve as a sensitive probe for MATBG model parameters, which are currently ambiguous as a result of unavoidable structural relaxation and twist-angle disorder. We present the layer Hall counterflow and the associated in-plane magnetization for three different MATBG continuum models, based on which many-body interacting models have been widely applied to study strong correlations in MATBG. At the single-particle level, our findings indicate notable differences in layer-projected Hall conductivity, both in magnitude and sign, between different MATBG continuum models. Furthermore, our self-consistent Hartree calculations, performed on each of these single-particle continuum models, reveal renormalized layer-projected Hall conductivity by the self-consistent Hartree field.

关键词： Electrical conductivity Electronic structure Hall effect Transport phenomena 2-dimensional systems Strongly correlated systems Twisted heterostructures Band structure methods Boltzmann theory k dot p method

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Breakdown of effective-medium theory by a photonic spin Hall effect

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Science China(physics,Mechanics & Astronomy) 2023年第11期66卷 145-154页

作者： Shuaijie Yuan Xinxing Zhou Yu Chen Yuhan Zhong Lijuan Sheng Hao Hu Hongsheng Chen Ido Kaminer Xiao Lin Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Synergetic Innovation Center for Quantum Effects and ApplicationsSchool of Physics and ElectronicsHunan Normal UniversityChangsha410081China International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology Engineering Technology Research Center for 2D Material Information Function Devices and Systems of Guangdong ProvinceInstitute of Microscale OptoelectronicsShenzhen UniversityShenzhen518060China Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and InstrumentationZJU-Hangzhou Global Scientific and Technological Innovation CenterZhejiang UniversityHangzhou310027China International Joint Innovation Center Electromagnetics Academy at Zhejiang UniversityZhejiang UniversityHaining314400China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore639798Singapore Key Laboratory of Radar Imaging and Microwave Photonics Ministry of EducationCollege of Electronic and Information EngineeringNanjing University of Aeronautics and AstronauticsNanjing211106China Key Laboratory of Advanced Micro/Nano Electronic Devices&Smart Systems of Zhejiang Jinhua Institute of Zhejiang UniversityZhejiang UniversityJinhua321099China Shaoxing Institute of Zhejiang University Zhejiang UniversityShaoxing312000China Department of Electrical Engineering Technion-Israel Institute of TechnologyHaifa32000Israel

Effective-medium theory pertains to the theoretical modelling of homogenization,which aims to replace an inhomogeneous structure of subwavelength-scale constituents with a homogeneous effective *** effective-medium theory is fundamental to various realms,including electromagnetics and material science,since it can largely decrease the complexity in the exploration of light-matter interactions by providing simple acceptable ***,the effective-medium theory is thought to be applicable to any all-dielectric system with deep-subwavelength constituents,under the condition that the effective medium does not have a critical angle,at which the total internal reflection *** we reveal a fundamental breakdown of the effective-medium theory that can be applied in very general conditions:showing it for deep-subwavelength all-dielectric multilayers even without a critical *** finding relies on an exotic photonic spin Hall effect,which is shown to be ultrasensitive to the stacking order of deep-subwavelength dielectric layers,since the spin-orbit interaction of light is dependent on slight phase accumulations during the wave *** results indicate that the photonic spin Hall effect could provide a promising and powerful tool for measuring structural defects for all-dielectric systems even in the extreme nanometer scale.

关键词： photonic spin Hall effect effective-medium theory spin-orbit interaction of light

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First passage times for continuous quantum measurement currents

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Physical Review A 2024年第5期109卷 L050202-L050202页

作者： Michael J. Kewming Anthony Kiely Steve Campbell Gabriel T. Landi School of Physics Trinity College Dublin College Green Dublin 2 Ireland School of Physics University College Dublin Belfield Dublin 4 Ireland Centre for Quantum Engineering Science and Technology University College Dublin Belfield Dublin 4 Ireland Dahlem Center for Complex Quantum Systems Freie Universität Berlin Arnimallee 14 14195 Berlin Germany Department of Physics and Astronomy University of Rochester Rochester New York 14627 USA

The first passage time (FPT) is the time taken for a stochastic process to reach a desired threshold. In this Letter we address the FPT of the stochastic measurement current in the case of continuously measured quantum systems. We find that our approach, based on a charge-resolved master equation related to full-counting statistics of charge detection, enables efficient and analytical computation of the FPT. We develop a versatile framework applicable to quantum jump unraveling and quantum diffusion scenarios, demonstrating that the FPT can be obtained by introducing absorbing boundary conditions. Our framework is demonstrated with two relevant examples: First, we examine the tightness of recently proposed kinetic uncertainty relations for quantum jumps, which place bounds on the signal-to-noise ratio of the FPT. Second, we investigate the usage of qubits as threshold detectors for Rabi pulses, showing how our method can optimize detection probability while minimizing false positives. This Letter offers insights into the applications of the FPT for continuous measurements including the signal-to-noise ratio bounds and false positive minimization strategies, advancing quantum information processing applications.

关键词： Escape problems Noise quantum control quantum measurements Random walks Stochastic inference Uncertainty relation Weak values & weak measurements Fokker–Planck equation Full counting statistics Lindblad equation Master equation quantum Monte Carlo Stochastic analysis Stochastic differential equations Time series analysis

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Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexagonal Boron Nitride for Integrated quantum Photonics

Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexa...

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CLEO: Science and Innovations in CLEO 2024, CLEO: S and I 2024 - Part of Conference on Lasers and Electro-Optics

作者： Roberts, Henry C. Waseem, Aadil Wicker, Scott A. Abudayyeh, Hamza Kim, Dong Seob Liu, Zhida Randolph, Steven Li, Xiaoqin Li, Xiuling Department of Electrical and Computer Engineering Microelectronics Research Center The University of Texas at Austin 10100 Harry Ransom Trail AustinTX78758 United States Department of Physics Center for Complex Quantum Systems Center for Dynamics Control of Materials Texas Materials Institute The University of Texas at Austin 2515 Speedway AustinTX78712 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37830 United States

We report a new approach to generate waveguide-coupled emission from deterministically implanted boron vacancy spin defects in hBN using single-crystal AlN-on-sapphire ring resonators. This facilitates the eventual development of hBN-based integrated quantum technologies. © Optica Publishing Group 2024

关键词： Single crystals

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Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexagonal Boron Nitride for Integrated quantum Photonics

Aluminum Nitride Ring Resonator-Coupled Spin Defects in Hexa...

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2024 Conference on Lasers and Electro-Optics, CLEO 2024

作者： Roberts, Henry C. Waseem, Aadil Wicker, Scott A. Abudayyeh, Hamza Kim, Dong Seob Liu, Zhida Randolph, Steven Li, Xiaoqin Li, Xiuling Department of Electrical and Computer Engineering Microelectronics Research Center The University of Texas at Austin 10100 Harry Ransom Trail AustinTX78758 United States Department of Physics Center for Complex Quantum Systems Center for Dynamics and Control of Materials Texas Materials Institute The University of Texas at Austin 2515 Speedway AustinTX78712 United States Center for Nanophase Materials Sciences Oak Ridge National Laboratory Oak RidgeTN37830 United States

ISBN: (纸本)9781957171395

关键词： Aluminum nitride

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