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Orthogonality and distinguishability: Criterion for local distinguishability of arbitrary orthogonal states

Physical Review A 2003年第6期68卷 062107-062107页

作者： Ping-Xing Chen Cheng-Zu Li Department of Applied Physics National University of Defense Technology Changsha 410073 People’s Republic of China Laboratory of Quantum Communication and Quantum Computation University of Science and Technology of China Hefei 230026 People’s Republic of China

We consider the relation between the orthogonality and the distinguishability of a set of arbitrary states (including multipartite states). It is shown that if a set of arbitrary states can be distinguished by local operations and classical communication (LOCC), each of the states can be written as a linear combination of product vectors such that all product vectors of one of the states are orthogonal to the other states. With this result we then prove a simple necessary condition for LOCC distinguishability of a class of orthogonal states. These conclusions may be useful in discussing the distinguishability of orthogonal quantum states further, understanding the essence of nonlocality and discussing the distillation of entanglement.

关键词： Quantum theory

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New dark matter candidate in the symmetric SSM

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The European Physical Journal C 2023年第11期83卷 1-8页

作者： Yang, Jin-Lei Yang, Zhong-Jun Yang, Xiu-Yi Zhang, Hai-Bin Feng, Tai-Fu Department of Physics Hebei University Baoding China Key Laboratory of High-precision Computation and Application of Quantum Field Theory of Hebei Province Baoding China Department of Physics Chongqing Key Laboratory for Strongly Coupled Physics Chongqing University Chongqing China Department of Science University of Science and Technology Liaoning Anshan China

The B-L symmetric SUSY model (B-LSSM) introduces a new $$Z'$$ gauge boson and two singlet scalars, which indicates there are more neutralinos in the B-LSSM comparing with the minimal SUSY extension of standard model (MSSM). These new neutralinos provide more dark matter (DM) candidates in the B-LSSM, we find that the super partner of the new scalar singlet can serve as the lightest supersymmetric particle (LSP) and be considered as a DM candidate. The properties of this new DM candidate are analyzed in this work. Taking into account the experimental constraints on Higgs boson mass, B meson rare decays and muon anomalous magnetic dipole moment, the numerical results are obtained and presented. The properties of new DM candidate in the B-LSSM satisfy the observed relic density $$\Omega h^2$$ and comply with the latest upper bounds on $$\sigma _\textrm{SI}^{\chi _1^0-n}$$ , and its mass is expected to greater than $$80\;\textrm{GeV}$$ approximately.

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Spin-orbit coupling and operation of multivalley spin qubits

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Physical Review B 2015年第20期92卷 201401(R)-201401(R)页

作者： M. Veldhorst R. Ruskov C. H. Yang J. C. C. Hwang F. E. Hudson M. E. Flatté C. Tahan K. M. Itoh A. Morello A. S. Dzurak Centre for Quantum Computation and Communication Technology School of Electrical Engineering and Telecommunications The University of New South Wales Sydney NSW 2052 Australia Laboratory for Physical Sciences 8050 Greenmead Drive College Park Maryland 20740 USA Department of Physics and Astronomy University of Iowa Iowa City Iowa 52242 USA School of Fundamental Science and Technology Keio University 3-14-1 Hiyoshi Kohoku-ku Yokohama 223-8522 Japan

Spin qubits composed of either one or three electrons are realized in a quantum dot formed at a Si/SiO2 interface in isotopically enriched silicon. Using pulsed electron-spin resonance, we perform coherent control of both types of qubits, addressing them via an electric field dependent g factor. We perform randomized benchmarking and find that both qubits can be operated with high fidelity. Surprisingly, we find that the g factors of the one-electron and three-electron qubits have an approximately linear but opposite dependence as a function of the applied dc electric field. We develop a theory to explain this g-factor behavior based on the spin-valley coupling that results from the sharp interface. The outer “shell” electron in the three-electron qubit exists in the higher of the two available conduction-band valley states, in contrast with the one-electron case, where the electron is in the lower valley. We formulate a modified effective mass theory and propose that intervalley spin-flip tunneling dominates over intravalley spin flips in this system, leading to a direct correlation between the spin-orbit coupling parameters and the g factors in the two valleys. In addition to offering all-electrical tuning for single-qubit gates, the g-factor physics revealed here for one-electron and three-electron qubits offers potential opportunities for different qubit control approaches.

关键词： QUANTUM computing ELECTRIC fields QUBITS ELECTROMAGNETIC theory ELECTRONS

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Zeeman and hyperfine interactions of a single Er3+167 ion in Si

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Physical Review B 2022年第23期105卷 235306-235306页

作者： Jiliang Yang Wenda Fan Yangbo Zhang Changkui Duan Gabriele G. de Boo Rose L. Ahlefeldt Jevon J. Longdell Brett C. Johnson Jeffrey C. McCallum Matthew J. Sellars Sven Rogge Chunming Yin Jiangfeng Du CAS Key Laboratory of Microscale Magnetic Resonance and School of Physical Sciences University of Science and Technology of China Hefei 230026 China CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 China Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales NSW 2052 Australia Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics Australian National University ACT 0200 Australia The Dodd-Walls Centre for Photonic and Quantum Technologies Department of Physics University of Otago Dunedin 9016 New Zealand Centre of Excellence for Quantum Computation and Communication Technology School of Engineering RMIT University Victoria 3001 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne Victoria 3010 Australia Hefei National Laboratory Hefei 230088 China

Er-doped Si is a promising candidate for quantum information applications due to its telecom wavelength optical transition and its compatibility with Si nanofabrication technologies. Recent spectroscopic studies based on photoluminescence excitation have shown multiple well-defined lattice sites that Er occupies in Si. Here we report a measurement of the Zeeman and hyperfine tensors of a single Er3+167 ion in Si. All the obtained tensors are highly anisotropic with the largest value principal axes aligning in nearly the same direction, and the trace of the lowest crystal field level g-tensor is 17.78±0.40. The results indicate that this specific Er site is likely to be a distorted cubic site that exhibits monoclinic (C1) symmetry. Finally, zero first-order-Zeeman fields are identified for this site and could be used to reduce decoherence of hyperfine spin states in future experiments.

关键词： Fine & hyperfine structure Zeeman effect Rare-earth doped crystals Single-electron transistors Optical spectroscopy

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Triplet Acceptors with a D-A Structure and Twisted Conformation for Efficient Organic Solar Cells

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Angewandte Chemie 2020年第35期132卷 15153-15159页

作者： Qin L. Liu X. Zhang X. Yu J. Yang L. Zhao F. Huang M. Wang K. Wu X. Li Y. Chen H. Xia J. Lu X. Gao F. Yi Y. Huang H. Center of Materials Science and Optoelectronics Engineering College of Materials Science and Opto-Electronic Technology & CAS Center for Excellence in Topological Quantum Computation & CAS Key Laboratory of Vacuum Physics University of Chinese Academy of Sciences Beijing 100049 China Department of Physics Chemistry and Biology (IFM) Linköping University Linköping 58183 Sweden Key Laboratory of Luminescence and Optical Information Ministry of Education School of Science Beijing Jiaotong University Beijing 100044 China Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Organic Solids CAS Research/Education Center for Excellence in Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Center of Smart Materials and Devices School of Chemistry Chemical Engineering and Life Science Wuhan University of Technology Wuhan 430070 China Department of Physics The Chinese University of Hong Kong New Territories Hong Kong

Triplet acceptors have been developed to construct high-performance organic solar cells (OSCs) as the long lifetime and diffusion range of triplet excitons may dissociate into free charges instead of net recombination when the energy levels of the lowest triplet state (T1) are close to those of charge-transfer states (3CT). The current triplet acceptors were designed by introducing heavy atoms to enhance the intersystem crossing, limiting their applications. Herein, two twisted acceptors without heavy atoms, analogues of Y6, constructed with large π-conjugated core and D-A structure, were confirmed to be triplet materials, leading to high-performance OSCs. The mechanism of triplet excitons were investigated to show that the twisted and D-A structures result in large spin–orbit coupling (SOC) and small energy gap between the singlet and triplet states, and thus efficient intersystem crossing. Moreover, the energy level of T1 is close to 3CT, facilitating the split of triplet exciton to free charges. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA

关键词： D-A structures long lifetime excitons organic solar cells triplet acceptors twisted conformation

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Linear Gaussian quantum state smoothing: Understanding the optimal unravelings for Alice to estimate Bob's state

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Physical Review A 2021年第1期103卷 012213-012213页

作者： Kiarn T. Laverick Areeya Chantasri Howard M. Wiseman Centre for Quantum Computation and Communication Technology (Australian Research Council) Centre for Quantum Dynamics Griffith University Nathan Queensland 4111 Australia Optical and Quantum Physics Laboratory Department of Physics Faculty of Science Mahidol University Bangkok 10140 Thailand

Quantum state smoothing is a technique to construct an estimate of the quantum state at a particular time, conditioned on a measurement record from both before and after that time. The technique assumes that an observer, Alice, monitors part of the environment of a quantum system and that the remaining part of the environment, unobserved by Alice, is measured by a secondary observer, Bob, who may have a choice in how he monitors it. The effect of Bob's measurement choice on the effectiveness of Alice's smoothing has been studied in a number of recent papers. Here we expand upon the Letter which introduced linear Gaussian quantum (LGQ) state smoothing [Phys. Rev. Lett. 122, 190402 (2019)]. In the current paper we provide a more detailed derivation of the LGQ smoothing equations and address an open question about Bob's optimal measurement strategy. Specifically, we develop a simple hypothesis that allows one to approximate the optimal measurement choice for Bob given Alice's measurement choice. By “optimal choice” we mean the choice for Bob that will maximize the purity improvement of Alice's smoothed state compared to her filtered state (an estimated state based only on Alice's past measurement record). The hypothesis, that Bob should choose his measurement so that he observes the back-action on the system from Alice's measurement, seems contrary to one's intuition about quantum state smoothing. Nevertheless, we show that it works even beyond a linear Gaussian setting.

关键词： Open quantum systems Quantum measurements Quantum states of light Quantum stochastic processes

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Speedup in classical simulation of Gaussian boson sampling

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science Bulletin 2020年第10期65卷 832-841,M0004页

作者： Bujiao Wu Bin Cheng Fei Jia Jialin Zhang Man-Hong Yung Xiaoming Sun Institute of Computing Technology Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Institute for Quantum Science and Engineering Department of PhysicsSouthern University of Science and TechnologyShenzhen 518055China Shenzhen Key Laboratory of Quantum Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Central Research Institute Huawei TechnologiesShenzhen 518129China CAS Center of Excellence in Topological Quantum Computation Beijing 100190China

Gaussian boson sampling is an alternative model for demonstrating quantum computational supremacy,where squeezed states are injected into every input mode, instead of applying single photons as in the case of standard boson sampling. Here by analyzing numerically the computational costs, we establish a lower bound for achieving quantum computational supremacy for a class of Gaussian bosonsampling problems. Specifically, we propose a more efficient method for calculating the transition probabilities, leading to a significant reduction of the simulation costs. Particularly, our numerical results indicate that one can simulate up to 18 photons for Gaussian boson sampling at the output subspace on a normal laptop, 20 photons on a commercial workstation with 256 cores, and about 30 photons for supercomputers. These numbers are significantly smaller than those in standard boson sampling, suggesting that Gaussian boson sampling could be experimentally-friendly for demonstrating quantum computational supremacy.

关键词： Gaussian boson sampling Classical simulation Hafnian Probability distribution Marginal distribution Quantum optics

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Fluctuating magnetic droplets immersed in a sea of quantum spin liquid

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The Innovation 2023年第5期4卷 33-40页

作者： Zihao Zhu Binglin Pan Linpeng Nie Jiamin Ni Yanxing Yang Changsheng Chen Chengyu Jiang Yeyu Huang Erjian Cheng Yunjie Yu Jianjian Miao Adrian D.Hilier Xianhui Chen Tao Wu Yi Zhou Shiyan Li Lei Shu State Key Laboratory of Surface Phys ics and Department of PhysicsFudan UniversityShanghai 200433China CAS Key Laboratory of Stronglycoupled Quantum Matter Physics Department of PhysicsUniversity of Science and Technology of ChinaHefeiAnhui 230026China Department of Physics the University of Hong KongHong KongChina ISIS Pulsed Neutron and Muon Source STFC Rutherford Appleton LaboratoryHarwell CampusDidcotOxfordshire 0X110QXUK Collaborative Innovation Center of Advanced Micr ostructures Nanjing 210093China CAS Center for Excellence in Superconducting Electronics(CENSE) Shanghai 200050China Institute of Physics and Beijing National Laboratory for Condensed Matter Physics Chinese Academy of SciencesBeijing 100190China Songshan Lake Materials Laboratory DongguanGuangdong 523808China Kavli Institute for Theoretical Sciences and CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China Shanghai Research Center for Quantum Sciences Shanghai 201315China

The search of quantum spin liquid(QSL),an exotic magnetic state with strongly fluctuating and highly entangled spins down to zero temperature,is a main theme in current condensed matter ***,there is no smoking gun evidence for deconfined spinons in any QSL candidate so *** disorders and competing exchange interactions may prevent the formation of an ideal QSL state on frustrated spin *** we report comprehensive and systematic measurements of the magnetic susceptibility,ultralow-temperature specific heat,muon spin relaxation(μSR),nuclear magnetic resonance(NMR),and thermal conductivity for NaYbSe2 single crystals,in which Yb3+ions with effective spin-1/2 form a perfect triangular *** these complementary techniques find no evidence of long-range magnetic order down to their respective base ***,specific heat,μSR,and NMR measurements suggest the coexistence of quasi-static and dynamic spins in *** scattering from these quasi-static spins may cause the absence of magnetic thermal ***,we propose a scenario of fluctuating ferrimagnetic droplets immersed in a sea of *** may be quite common on the way pursuing an ideal QSL,and provides a brand new platform to study how a QSL state survives impurities and coexists with other magnetically ordered states.

关键词： NMR immersed quantum

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Ultrashallow Junction Electrodes in Low-Loss Silicon Microring Resonators

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Physical Review Applied 2021年第4期15卷 044014-044014页

作者： Bin-Bin Xu Gabriele G. de Boo Brett C. Johnson Miloš Rančić Alvaro Casas Bedoya Blair Morrison Jeffrey C. McCallum Benjamin J. Eggleton Matthew J. Sellars Chunming Yin Sven Rogge Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of New South Wales Sydney NSW 2052 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Physics University of Melbourne Parkville Victoria 3010 Australia Centre of Excellence for Quantum Computation and Communication Technology School of Engineering RMIT University Melbourne Victoria 3001 Australia Centre of Excellence for Quantum Computation and Communication Technology Research School of Physics and Engineering Australian National University ACT Canberra 0200 Australia Institute of Photonics and Optical Science (IPOS) School of Physics The University of Sydney Camperdown NSW 2006 Australia The University of Sydney Nano Institute (Sydney Nano) The University of Sydney Camperdown NSW 2006 Australia CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics University of Science and Technology of China Hefei 230026 China

Electrodes in close proximity to an active area of a device are required for sufficient electrical control. The integration of such electrodes into optical devices can be challenging since low optical losses must be retained to realize high-quality operation. Here, we demonstrate that it is possible to place a metallic shallow phosphorus doped layer in a silicon microring cavity that can function at cryogenic temperatures. We verify that the shallow doping layer affects the local refractive index while inducing minimal losses with quality factors up to 105. This demonstration opens up a pathway to the integration of an electronic device, such as a single-electron transistor, into an optical circuit on the same material platform.

关键词： Electrical conductivity Integrated optics Nanophotonics Optoelectronics Devices Junctions Semiconductor microcavities Cavity resonators

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Entangling and cloning machine with increasing robustness against decoherence as the number of qubits increases

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Physical Review A 2005年第6期72卷 064303-064303页

作者： Shi-Biao Zheng Guang-Can Guo Laboratory of Quantum Communication and Quantum Computation University of Science and Technology of China Hefei 230026 P. R. China Department of Electronic Science and Applied Physics Fuzhou University Fuzhou 350002 P. R. China‡

We propose a machine for entangling multiple qubits and implementing cloning and anti-cloning. The operation speed increases with the number of qubits without a limitation and thus the operation becomes more and more robust against decoherence with the increase of the number of qubits. This is contrary to usual entangling machines and quantum information processors whose performance would deteriorate with the increase of the number of qubits due to decoherence. We illustrate the idea in the ion trap system, however it can also be realized in other systems, opening a new perspective for building a scalable machine for entanglement generation and quantum information processing.

关键词： MULTIPARTICLE ENTANGLEMENT QUANTUM CLONING THERMAL MOTION TRAPPED IONS GENERATION THEOREM STATES

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