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Chinese Physics B 2011年第8期20卷 23-29页

作者：周凤雪张理达祁义红钮月萍张敬涛龚尚庆 State Key Laboratory of High Field Laser Physics Shanghai Institute of Optics and Fine MechanicsChinese Academy of Sciences Department of Physics East China University of Science and Technology

This paper investigates the entanglement dynamics of a Heisenberg XY model for a two-spin system in the presence of a nonuniform magnetic field. The master equations and the concurrence evolution equations for the initial α state ave derived and analysed. It is shown that for the symmetric initial α state, only the nonuniform field can play a role in entanglement dynamics while the uniform field and the bath will not play such a role. For the asymmetric α state, the nonuniform field leads to the beat pattern oscillation of the concurrence evolution. The inhomogeneity of the field can enhance the entanglement by suppressing the decoherence effects of both the spin-orbit interaction and the spin bath.

关键词： quantum entanglement decoherence qubits Heisenberg model

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Electric field manipulation enhanced by strong spin-orbit coupling: promoting rare-earth ions as qubits

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National Science Review 2020年第10期7卷 1557-1563页

作者： Zheng Liu Ye-Xin Wang Yu-Hui Fang Si-Xue Qin Zhe-Ming Wang Shang-Da Jiang Song Gao Beijing National Laboratory of Molecular Science State Key Laboratory of Rare Earth Materials Chemistry and ApplicationsBeijing Key Laboratory of Magnetoelectric Materials and Devices College of Chemistry and Molecular Engineering Peking University Department of Physics Chongqing University Beijing Academy of Quantum Information Sciences School of Chemistry and Chemical Engineering South China University of Technology

Quantum information processing based on magnetic ions has potential for applications as the ions can be modified in their electronic properties and assembled by a variety of chemical methods. For these systems to achieve individual spin addressability and high energy efficiency, we exploited the electric field as a tool to manipulate the quantum behaviours of the rare-earth ion which has strong spin-orbit coupling. A Ce:YAG single crystal was employed with considerations to the dynamics and the symmetry requirements. The Stark effect of the Ce;ion was observed and measured. When demonstrated as a quantum phase gate, the electric field manipulation exhibited high efficiency which allowed up to 57 π/2 operations before decoherence with optimized field direction. It was also utilized to carry out quantum bang-bang control, as a method of dynamic decoupling, and the refined Deutsch-Jozsa algorithm. Our experiments highlighted rare-earth ions as potentially applicable qubits because they offer enhanced spin-electric coupling which enables high-efficiency quantum manipulation.

关键词： quantum coherent manipulation spin-orbit coupling spin-electric coupling rare-earth ions qubits

Experimentally Obtaining the Likeness of Two Unknown qubits on a Nuclear-Magnetic-Resonance Quantum Information Processor

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Chinese Physics Letters 2003年第10期20卷 1669-1671页

作者：薛飞杜江峰周先意韩荣典吴季辉 DepartmentofModernPhysics UniversityofScienceandTechnologyofChinaHefei230027 LaboratoryofStructureBiology UniversityofScienceandTechnologyofChinaHefei230027

We study the discrimination of quantum states from the other way around, i.e. the likeness of two quantum states. The fidelity is used to describe the likeness of two quantum states. Then we present a scheme to obtain the fidelity of two unknown qubits directly from the integral area of the spectra of the assistant qubit (spin) on a nuclear-magnetic-resonance quantum information processor. Finally, we demonstrate the scheme on a three-qubit quantum information processor. The experimental data are consistent with the theoretical expectation with an average error of 0.05, which confirms the scheme.

关键词：量子信息处理 QIP 量子态核子磁性谐振实验研究 qubits 自旋光谱

Tuning Entanglement Patterns in qubits Clusters

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Journal of Quantum Information Science 2013年第2期3卷 85-92页

作者： F. B. M. Dos Santos A. M. S. Macêdo Departamento de Física Universidade Estadual de Feira de Santana Feira de Santana Brasil Laboratório de Física Teórica e Computacional Departamento de Física Universidade Federal de Pernambuco Recife Brasil

We identify patterns of ground state entanglement, or quantum discord, in qubit clusters with three and four qubits, that are induced by varying the couplings between next-nearest neighbors in the clusters. We show that these entanglement patterns can be associated with continuous multiply connected regions in parameter space, on which entanglement quantifiers, such as the pairwise concurrence, exhibit a particular type of behavior as a function of the couplings between next-nearest neighbors in the cluster. We present the distinct patterns in diagrams in parameter space with continuous boundary lines and we associate each pattern to a specific type of pure quantum correlation. We propose this procedure as a simple method to identify useful classes of pure quantum correlations in qubit networks.

关键词： Entanglement Patterns qubits

Study of Decoherence of Entangled States Made up of Two Basic States in a Linear Chain of Three qubits

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Journal of Modern Physics 2015年第11期6卷 1701-1710页

作者： Gustavo López Velázquez Gustavo Montes Cabrera Departamento de Física Universidad de Guadalajara Blvd. Marcelino García Barragan y Calzada Olímpica Guadalajara Mexico

Using Lindblad approach to study decoherence of quantum systems, we study the decoherence and decay of entangled states, formed by two basic states of a chain of thee qubits. We look on these states for a possible regular dependence on their decay as a function of their energy separation between the basic states under different types of environments. We didn’t find regular or significant dependence on this energy separation for the type of environment considered.

关键词： Study of Decoherence of Entangled States Made up of Two Basic States in a Linear Chain of Three qubits Decoherence Entangled States Three Quits Linear Chain

Tailoring Quantum Correlations of a Coupled Central Two qubits Soaked in a Finite Temperature Antiferromagnetic Environment with Frequency Gap

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Journal of Quantum Information Science 2014年第4期4卷 201-213页

作者： Lukong Cornelius Fai Ngwa Engelbert Afuoti Georges Collince Fouokeng Jules Casimir Ngana Kuetche Martin Tchoffo Mesoscopic and Multilayer Structures Laboratory Department of Physics University of Dschang Dschang Cameroon Department of Thermal Engineering and Energy Douala University Institute of Technology Douala Cameroon Department of Physics University of Buea Buea Cameroon

We revisit the quantum features of an anti-ferromagnetic (AF) spin environment at finite temperature with gap in its frequency spectrum, on the dynamics quantum correlations of a coupled central two qubits system with Dzyaloshinskii-Moriya (DM) interaction, prepared in two entangled Bell states. Using entanglement and quantum discord as quantum meters of decoherence, the prepared entangled states are classified as robust or fragile relative to the degree of information leakage to the AF environment. By tailoring the size of the frequency gap, anisotropy field strength and induced field, due to system AF spin environment coupling, size of the AF environment and DM interaction parameter, a decoherence-free sub-space can be accessed for efficient execution of quantum protocols encoded in the entangled states.

关键词： Anti-Ferromagnetic Lattice Anisotropy Field Magnetic Field Quantum Correlations Central Two qubits

Identification of the phosphorus-doping defect in MgS as a potential qubit

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Chinese Physics B 2022年第10期31卷 261-267页

作者： Jijun Huang Xueling Lei Department of Physics Jiangxi Normal UniversityNanchang 330022China

The P_(S) defect is obtained by replacing one S atom with one P atom in the wide-bandgap semiconductor Mg *** on first-principles calculations,the formation energy,defect levels,and electronic structure of the PSdefect in different charge states are *** predict that the neutral P^(0)_(S)and positively charged P^(+1)_(S)are the plausible qubit candidates for the construction of quantum systems,since they maintain the spin conservation during optical excited *** zero-phonon lines at the P^(0)_(S)and P^(+1)_(S)defects are 0.43 e V and 0.21 e V,respectively,which fall in the infrared *** addition,the zero-field splitting parameter D of the P^(+1)_(S)with spin-triplet is 2920 MHz,which is in the range of microwave,showing that the P^(+1)_(S)defect can be manipulated by ***,the principal values of the hyperfine tensor are examined,it is found that they decay exponentially with the distance from the defect site.

关键词： point defects MgS semiconductor qubits first-principles calculations

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Spin manipulation in semiconductor quantum dots qubit

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Chinese Physics B 2018年第9期27卷 1-14页

作者： Ke Wang Hai-Ou L Ming Xiao Gang Cao and Guo-Ping Guo CAS Key Laboratory of Quantum Information University of Science and Technology of ChinaHefei 230026China

Thirty years of effort in semiconductor quantum dots has resulted in significant developments in the control of spin quantum bits（qubits）. The natural two-energy level of spin states provides a path toward quantum information processing. In particular, the experimental implementation of spin control with high fidelity provides the possibility of realizing quantum computing. In this review, we will discuss the basic elements of spin qubits in semiconductor quantum dots and summarize some important experiments that have demonstrated the direct manipulation of spin states with an applied electric field and/or magnetic field. The results of recent experiments on spin qubits reveal a bright future for quantum information processing.

关键词： semiconductor quantum dot qubits spin manipulation

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Determination of Relaxation Time of a Josephson Tunnel Junction

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Chinese Physics Letters 2008年第2期25卷 694-697页

作者：温学达于扬 National Laboratory of Solid State Microstructures Department of Physics Nanjing University Nanjing 210093

We propose a non-stationary method to measure the energy relaxation time of Josephson tunnel junctions from microwave enhanced escape phenomena. Compared with the previous methods, our method possesses simple and accurate features. Moreover, having determined the energy relaxation time, we can further obtain the coupling strength between the microwave source and the junction by changing the microwave power.

关键词： MACROSCOPIC QUANTUM STATES LEVEL QUANTIZATION OSCILLATIONS LIFETIME qubits

Quantum Entanglement in a System of Two Spatially Separated Atoms Coupled to the Thermal Reservoir

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Chinese Physics Letters 2006年第12期23卷 3138-3141页

作者：廖湘萍方卯发郑小娟蔡建武 Department of Physics Hunan Normal University Changsha 410081 Department of Physics and Electronics Zhuzhou Teachers' College Zhuzhou 412007 Department of Physics Hunan Industrial University Zhuzhou 412000

We study quantum entanglement between two spatially separated atoms coupled to the thermal reservoir. The influences of the initial state of the system, the atomic frequency difference and the mean number of the thermal field on the entanglement are examined. The results show that the maximum of the entanglement obtained with nonidentical atoms is greater than that obtained with identical atoms. The degree of entanglement is progressively decreased with the increase of the thermal noise. Interestingly, the two atoms can be easily entangled even when the two atoms are initially prepared in the most mixed states.

关键词： SPONTANEOUS EMISSION 2-ATOM SYSTEMS CAVITY DECOHERENCE RADIATION STATES FIELD DISSIPATION GENERATION qubits