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Memory-effect-induced macroscopic-microscopic entanglement

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Physical Review A 2016年第1期94卷 012334-012334页

作者： Qingxia Mu Xinyu Zhao Ting Yu Mathematics and Physics Department North China Electric Power University Beijing 102206 China Center for Controlled Quantum Systems and Department of Physics and Engineering Physics Stevens Institute of Technology Hoboken New Jersey 07030 USA Beijing Computational Science Research Center Beijing 100094 China

We study optomechanical entanglement between an optical cavity field and a movable mirror coupled to a non-Markovian environment. The non-Markovian quantum-state diffusion approach and the non-Markovian master equation are shown to be useful in investigating entanglement generation between the cavity field and the movable mirror. The simple model presented in this paper demonstrates several interesting properties of optomechanical entanglement that are associated with environment memory effects. It is evident that the effective environment central frequency can be used to modulate the optomechanical entanglement. In addition, we show that the maximum entanglement may be achieved by properly choosing the effective detuning, which is significantly dependent on the strength of the memory effect of the environment.

关键词： Entanglement production

Dzyaloshinskii-Moriya interaction across antiferromagnet/ferromagnet interface

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arXiv 2017年

作者： Ma, Xin Yu, Guoqiang Razavi, Seyed A. Sasaki, Stephen S. Li, Xiang Hao, Kai Tolbert, Sarah H. Wang, Kang L. Li, Xiaoqin Department of Physics Center for Quantum systems University of Texas at Austin AustinTX78712 United States Department of Electrical Engineering University of California Los AngelesCA90095 United States Department of Chemistry and Biochemistry University of California Los AngelesCA90095 United States Department of Physics University of California Los AngelesCA90095 United States

The antiferromagnet (AFM)/ferromagnet (FM) interfaces are of central importance in recently developed pure electric or ultrafast control of FM spins, where the underlying mechanisms remain unresolved. Here we report the direct observation of Dzyaloshinskii-Moriya interaction (DMI) across the AFM/FM interface of IrMn/CoFeB thin films. The interfacial DMI is quantitatively measured from the asymmetric spin-wave dispersion in the FM layer using Brillouin light scattering. The DMI strength is enhanced by a factor of 7 with increasing IrMn layer thickness in the range of 1- 7.5 nm. Our findings provide deeper insight into the coupling at AFM/FM interface and may stimulate new device concepts utilizing chiral spin textures such as magnetic skyrmions in AFM/FM heterostructures. Copyright © 2017, The Authors. All rights reserved.

关键词： Antiferromagnetic materials

Homogeneous-material-based calibration method for correcting laser-induced breakdown spectroscopy measurement-error bias in the case of dust pollution

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Applied optics 2017年第35期56卷 9644-9648页

作者： Yang Zhao Lei Zhang Wangbao Yin Jiajia Hou Zhe Wang Zongyu Hou Weiguang Ma Lei Dong Guangye Yang Liantuan Xiao Suotang Jia State Key Laboratory of Quantum Optics and Quantum Optics Devices Institute of Laser Spectroscopy Shanxi University Taiyuan 030006 China State Key Laboratory of Power Systems Department of Thermal Engineering Tsinghua-BP Clean Energy Center Tsinghua University Beijing 100083 China Physics college Shanxi Medical University Taiyuan 030002 China

A calibration method based on homogeneous material for correcting laser-induced breakdown spectroscopy (LIBS) measurement-error bias in the case of dust pollution under laboratory conditions is proposed. The measured plasma spectra of the sample can be corrected by measuring the spectral integral of the homogeneous material. Thus, we can effectively minimize the dust pollution effect on LIBS and guarantee its precision. Results show that the mean absolute errors of CaO, MgO, FeO, AlO, and SiO in cement samples are decreased notably from 1.02%, 0.06%, 0.15%, 0.57%, and 0.80% to 0.41%, 0.02%, 0.04%, 0.35%, and 0.39%, respectively. Combination of this calibration method with the traditional optical dustproof methods will significantly extend the LIBS equipment maintenance cycle and make preliminary preparations for the next practical industrial application.

关键词： Analytical techniques Laser energy Laser induced breakdown Optical components Optical elements Spectroscopy

Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems

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arXiv 2019年

作者： Tancogne-Dejean, Nicolas Oliveira, Micael J.T. Andrade, Xavier Appel, Heiko Borca, Carlos H. Le Breton, Guillaume Buchholz, Florian Castro, Alberto Corni, Stefano Correa, Alfredo A. de Giovannini, Umberto Delgado, Alain Eich, Florian G. Flick, Johannes Gil, Gabriel Gomez, Adrián Helbig, Nicole Hübener, Hannes Jestädt, René Jornet-Somoza, Joaquim Larsen, Ask H. Lebedeva, Irina V. Lüders, Martin Marques, Miguel A.L. Ohlmann, Sebastian T. Pipolo, Silvio Rampp, Markus Rozzi, Carlo A. Strubbe, David A. Sato, Shunsuke A. Schäfer, Christian Theophilou, Iris Welden, Alicia Rubio, Angel Max Planck Institute for the Structure and Dynamics of Matter Luruper Chaussee 149 HamburgD-22761 Germany Quantum Simulations Group Lawrence Livermore National Laboratory LivermoreCA94551 United States Département de Physique École Normale Supérieure de Lyon 46 Allée d’Italie Lyon Cedex 07 France Institute for Biocomputation and Physics of Complex Systems University of Zaragoza Calle Mariano Esquillor Zaragoza50018 Spain ARAID Foundation Avda. de Ranillas 1-D Zaragoza50018 Spain Dipartimento di Scienze Chimiche Università degli studi di Padova via F. Marzolo 1 Padova35131 Italy CNR – Istituto Nanoscienze via Campi 213a Modena41125 Italy Xanadu 777 Bay Street TorontoONM5G 2C8 Canada John A. Paulson School of Engineering and Applied Sciences Harvard University CambridgeMA02138 United States Center for Computational Quantum Physics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Instituto de Cibernética Matemática y Física Calle E 309 La Habana10400 Cuba Nanomat/Qmat/CESAM and ETSF Université de Liège Sart-TilmanB-4000 Belgium Nano-Bio Spectroscopy Group ETSF Universidad del País Vasco San Sebastián20018 Spain 06120 Germany Max Planck Computing and Data Facility Gießenbachstraße 2 Garching85741 Germany Universit de Lille CNRS Centrale Lille ENSCL Universit d Artois UMR 8181 UCCS Unit de Catalyse et Chimie du Solide LilleF-59000 France Department of Physics School of Natural Sciences University of California MercedCA95343 United States Center for Computational Sciences University of Tsukuba Tsukuba305-8577 Japan

Over the last years extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high-degree of precision. An appealing and challenging route towards engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind, providing an unique framework allowing to describe non-equilibrium phenomena in molecular complexes, low dimensional materials, and extended systems by accounting for electronic, ionic, and photon quantum mechanical effects within a generalized time-dependent density functional theory framework. The present article aims to present the new features that have been implemented over the last few years, including technical developments related to performance and massive parallelism. We also describe the major theoretical developments to address ultrafast light-driven processes, like the new theoretical framework of quantum electrodynamics density-functional formalism (QEDFT) for the description of novel light-matter hybrid states. Those advances, and other being released soon as part of the Octopus package, will enable the scientific community to simulate and characterize spatial and time-resolved spectroscopies, ultrafast phenomena in molecules and materials, and new emergent states of matter (QED-materials). Copyright © 2019, The Authors. All rights reserved.

关键词： Density functional theory

Spin of a multielectron quantum dot and its interaction with a neighboring electron

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arXiv 2017年

作者： Malinowski, Filip K. Martins, Frederico Smith, Thomas B. Bartlett, Stephen D. Doherty, Andrew C. Nissen, Peter D. Fallahi, Saeed Gardner, Geoffrey C. Manfra, Michael J. Marcus, Charles M. Kuemmeth, Ferdinand Center for Quantum Devices and Station Q Copenhagen Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Centre for Engineered Quantum Systems School of Physics University of Sydney SydneyNSW2006 Australia Department of Physics and Astronomy Station Q Purdue Birck Nanotechnology Center Purdue University West LafayetteIN47907 United States School of Electrical and Computer Engineering School of Materials Engineering Purdue University West LafayetteIN47907 United States

We investigate the spin of a multielectron GaAs quantum dot in a sequence of nine charge occupancies, by exchange coupling the multielectron dot to a neighboring two-electron double quantum dot. For all nine occupancies, we make use of a leakage spectroscopy technique to reconstruct the spectrum of spin states in the vicinity of the interdot charge transition between a single- and a multielectron quantum dot. In the same regime we also perform time-resolved measurements of coherent exchange oscillations between the single- and multielectron quantum dot. With these measurements, we identify distinct characteristics of the multielectron spin state, depending on whether the dot’s occupancy is even or odd. For three out of four even occupancies we do not observe any exchange interaction with the single quantum dot, indicating a spin-0 ground state. For the one remaining even occupancy, we observe an exchange interaction that we associate with a spin-1 multielectron quantum dot ground state. For all five of the odd occupancies, we observe an exchange interaction associated with a spin-1/2 ground state. For three of these odd occupancies, we clearly demonstrate that the exchange interaction changes sign in the vicinity of the charge transition. For one of these, the exchange interaction is negative (i.e. triplet-preferring) beyond the interdot charge transition, consistent with the observed spin-1 for the next (even) occupancy. Our experimental results are interpreted through the use of a Hubbard model involving two orbitals of the multielectron quantum dot. Allowing for the spin correlation energy (i.e. including a term favoring Hund’s rules) and different tunnel coupling to different orbitals, we qualitatively reproduce the measured exchange profiles for all occupancies. Copyright © 2017, The Authors. All rights reserved.

关键词： Semiconductor quantum dots

Kinetic inductance neutron detector operated at near critical temperature

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Journal of physics: Conference Series 2020年第1期1590卷

作者： The Dang Vu Kazuma Nishimura Hiroaki Shishido Masahide Harada Kenichi Oikawa Shigeyuki Miyajima Mutsuo Hidaka Takayuki Oku Kazuhiko Soyama Kazuya Aizawa Kenji M Kojima Tomio Koyama Alex Malins Masahiko Machida Takekazu Ishida Materials and Life Science Division J-PARC Center Japan Atomic Energy Agency Tokai Ibaraki 319-1195 Japan Department of Physics and Electronics Osaka Prefecture University Sakai Osaka 599-8531 Japan NanoSquare Research Institute Osaka Prefecture University Sakai Osaka 599-8570 Japan Advanced ICT Research Institute National Institute of Information and Communications Technology (NICT) Kobe Hyogo 651-2492 Japan National Institute of Advanced Industrial Science and Technology (AIST) Tsukuba Ibaraki 305-8568 Japan Centre for Molecular and Materials Science TRIUMF Vancouver BC V6T 2A3 and V6T 1Z4 Canada Division of Quantum and Radiation Engineering Osaka Prefecture University Sakai Osaka 599-8570 Japan Center for Computational Science and e-Systems Japan Atomic Energy Agency 178-4-4 Wakashiba Kashiwa Chiba 277-0871 Japan

We previously succeeded in constructing and demonstrating the capability of a neutron imaging system based on a superconducting current-biased kinetic inductance detector (CB-KID). In the present work, we systematically studied the characteristics of the superconducting neutron detector to improve the spatial resolution and detection efficiency. We found that the number of neutron detection events with CB-KID remarkably increased when the detector temperature increased from 4 K to the critical temperature Tc. We observed systematic changes of neutron signals as a function of the detector temperature from 4 K to Tc. We evaluated the detection efficiency of the CB-KID detector, and compared with PHITS Monte Carlo simulations, which modeled the sequential physical processes for the 10B(n,α)7Li reaction, the transport dynamics, and the energy deposition by particles including neutrons, 4He particles, 7Li particles, photons, and electrons.

关键词：

Topological quantum error correction in the Kitaev honeycomb model

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arXiv 2017年

作者： Lee, Yi-Chan Brell, Courtney G. Flammia, Steven T. Centre for Engineered Quantum Systems School of Physics University of Sydney SydneyNSW2006 Australia Centre for Quantum Software and Information Faculty of Engineering and Information Technology University of Technology Sydney NSW2007 Australia Physics Department National Tsing-Hua University Hsinchu300 Taiwan Institut für Theoretische Physik Leibniz Universität Hannover Appelstraße 2 Hannover30167 Germany Perimeter Institute for Theoretical Physics WaterlooON Canada Center for Theoretical Physics Massachusetts Institute of Technology CambridgeMA United States

The Kitaev honeycomb model is an approximate topological quantum error correcting code in the same phase as the toric code, but requiring only a 2-body Hamiltonian. As a frustrated spin model, it is well outside the commuting models of topological quantum codes that are typically studied, but its exact solubility makes it more amenable to analysis of effects arising in this noncommutative setting than a generic topologically ordered Hamiltonian. Here we study quantum error correction in the honeycomb model using both analytic and numerical techniques. We first prove explicit exponential bounds on the approximate degeneracy, local indistinguishability, and correctability of the code space. These bounds are tighter than can be achieved using known general properties of topological phases. Our proofs are specialized to the honeycomb model, but some of the methods may nonetheless be of broader interest. Following this, we numerically study noise caused by thermalization processes in the perturbative regime close to the toric code renormalization group fixed point. The appearance of non-topological excitations in this setting has no significant effect on the error correction properties of the honeycomb model in the regimes we study. Although the behavior of this model is found to be qualitatively similar to that of the standard toric code in most regimes, we find numerical evidence of an interesting effect in the low-temperature, finite-size regime where a preferred lattice direction emerges and anyon diffusion is geometrically constrained. We expect this effect to yield an improvement in the scaling of the lifetime with system size as compared to the standard toric code. Copyright © 2017, The Authors. All rights reserved.

关键词： Hamiltonians

Tailoring semiconductor lateral multi-junctions for giant photoconductivity enhancement

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arXiv 2017年

作者： Tsai, Yutsung Chu, Zhaodong Han, Yimo Chuu, Chih-Piao Wu, Di Johnson, Alex Cheng, Fei Chou, Mei-Yin Muller, David A. Li, Xiaoqin Lai, Keji Shih, Chih-Kang Department of Physics Center for Complex Quantum Systems The University of Texas at Austin AustinTX78712 United States School of Applied and Engineering Physics Cornell University IthacaNY14853 United States Institute of Atomic and Molecular Sciences Academia Sinica Taipei10617 Taiwan Physics Division National Center for Theoretical Sciences Hsinchu Taiwan School of Physics Georgia Institute of Technology AtlantaGA30332 United States Kavli Institute at Cornell for Nanoscale Science IthacaNY14853 United States

Semiconductor heterostructures have played a critical role as the enabler for new science and technology. The emergence of transition metal dichalcogenides (TMDs) as atomically thin semiconductors has opened new frontiers in semiconductor heterostructures either by stacking different TMDs to form vertical heterojunctions or by stitching them laterally to form lateral heterojunctions via direct growth. In conventional semiconductor heterostructures, the design of multi-junctions is critical to achieve carrier confinement. Analogously, we report successful synthesis of monolayer WS2/WS2(1-x)Se2x/WS2 multi-junction lateral heterostructure via direct growth by chemical vapor deposition. The grown structures are characterized by Raman, photoluminescence, and annular dark-field scanning transmission electron microscopy to determine its lateral compositional profile. More importantly, using microwave impedance microscopy, we demonstrate that the local photoconductivity in the alloy region can be tailored and enhanced by 2 orders of magnitude over pure WS2. Finite element analysis confirms that this effect is due to the carrier diffusion and confinement into the alloy region. Our work exemplifies the technological potential of atomically thin lateral heterostructures in optoelectronic applications. Copyright © 2017, The Authors. All rights reserved.

关键词： Heterojunctions

On-Chip Microwave quantum Hall Circulator

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Physical Review X 2017年第1期7卷 011007-011007页

作者： A. C. Mahoney J. I. Colless S. J. Pauka J. M. Hornibrook J. D. Watson G. C. Gardner M. J. Manfra A. C. Doherty D. J. Reilly ARC Centre of Excellence for Engineered Quantum Systems School of Physics The University of Sydney Sydney New South Wales 2006 Australia Station Q Sydney The University of Sydney Sydney New South Wales 2006 Australia Department of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA Birck Nanotechnology Center School of Materials Engineering and School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA Station Q Purdue Purdue University West Lafayette Indiana 47907 USA

Circulators are nonreciprocal circuit elements that are integral to technologies including radar systems, microwave communication transceivers, and the readout of quantum information devices. Their nonreciprocity arises from the interference of microwaves over the centimeter scale of the signal wavelength, in the presence of bulky magnetic media that breaks time-reversal symmetry. Here, we realize a completely passive on-chip microwave circulator with size 1/1000th the wavelength by exploiting the chiral, “slow-light” response of a two-dimensional electron gas in the quantum Hall regime. For an integrated GaAs device with 330 μm diameter and about 1-GHz center frequency, a nonreciprocity of 25 dB is observed over a 50-MHz bandwidth. Furthermore, the nonreciprocity can be dynamically tuned by varying the voltage at the port, an aspect that may enable reconfigurable passive routing of microwave signals on chip.

关键词： Edge states Plasma oscillations Plasmons quantum control quantum information processing Semiconductors