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Implementing Entanglement Swapping with Trapped Atoms via Cavity Decay

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Chinese Physics Letters 2004年第8期21卷 1525-1528页

作者：林秀敏喻擘周正威薛鹏郭光灿 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026

With trapped atoms, we propose an experimental scheme to implement entanglement swapping based on adiabatic passage and the detection of cavity decay. This scheme is inherently robust to diverse sources of noise, such as atomic spontaneous emission, or detector inefficiency. The advantages make it realizable with the current experimental technology.

关键词： Atoms

Squeezing and Entanglement in Continuous Variable Systems

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Chinese Physics Letters 2004年第10期21卷 1877-1880页

作者：夏云杰郭光灿 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026

Based on total variance of a pair of Einstein–Podolsky–Rosen (EPR) type operators, the generalized EPR entangled states in continuous variable systems are defined. We show that such entangled states must correspond to two-mode squeezing states whether these states are Gaussian or not and whether they are pure or not. With help of the relation between the total variance and the entanglement, the degree of such entanglement is also defined. Through analysing some specific cases, we see that this method is very convenient and easy in practical applications. In addition, an entangled state with no squeezing is studied, which reveals that there certainly exists something unknown about entanglement in continuous variable systems.

关键词： Quantum optics

Ground-State Entanglement and Mixture in an XXZ Spin Chain

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Chinese Physics Letters 2005年第8期22卷 1829-1832页

作者：王成志李春先郭光灿 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026

We study the pairwise entanglement and mixture of a three-qubit XXZ spin chain in the ground state in the presence of an external magnetic field B. The effects of the magnetic field, the anisotropy and the temperature on the entanglement and mixture are considered, and entanglement versus the mixture of all the two-spin states is investigated. We find that the maximal entangled mixed state can be obtained in the considered system by controlling the magnetic field. Our results provide another way to generate maximally entangled mixed states.

关键词： Ground-State Entanglement China MEMS

A controlled Quantum Key Distribution Scheme with Three—Particle Entanglement

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Chinese Physics Letters 2003年第2期20卷 183-185页

作者：韩超薛鹏等 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026

We present a controlled quantum key distribution protocol with a certain entangled state to solve a special cryptographic task. Also, we provide a proof of security of this protocol by generalizing the proof of the mo... 详细信息

关键词： Quantum cryptography

Entangled States with Positive Partial Transpose in Any-Dimensional Quantum System

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Chinese Physics Letters 2005年第3期22卷 529-532页

作者：吴玉椿陈平形周正威郭光灿 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026//DepartmentofAppliedPhysicsNationalUniversityofDefenceTechnologyChangsha410073

It is well known that the positive partial transpose (PPT) criterion for determining separability is an operational separability criterion. However, in a high-dimensional (>6) situation, this criterion is not sufficient. How can we judge whether an entangled state in any high-dimensional quantum system is PPT or not? Here we propose a linear algebra method for checking the positivity of the partial transpose of a state and present a set of entangled mixed states with non-positive partial transpose.

关键词： Entangled States Positive Partial Transpose Any-Dimensional Quantum System

A “Which Way” Experiment of Two-Photon Interference

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Chinese Physics Letters 2005年第2期22卷 335-338页

作者：王琴黄运锋孙方稳张永生郭光灿 keylaboratoryofquantuminformation DepartmentofPhysicsUniversityofScienceandTechnologyofChinaHefei230026

It is well known that the indistinguishability of particles causes interference. We give a ``which way'' experiment of two-photon interference marked with polarization. The result shows that the greater the distinguishability of the path by which two-photon passes, the lower the fringe visibility will be, and this phenomenon will disappear when the path becomes completely distinguishable.

关键词：二光子干涉量子干涉测量方法极化作用 SPDC

Preparation of Two-Qutrit Entangled State in Cavity QED

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Chinese Physics Letters 2005年第6期22卷 1318-1320页

作者：林秀敏周正威吴玉椿王成志郭光灿 keylaboratoryofquantuminformation DepartmentofPhysicsUniversityofScienceandTechnologyofChinaHefei230026

We propose a scheme to generate a 3×3-dimensional maximally entangled state of two particles. Two three-level atoms interact with a strongly detuned cavity so that the cavity is only virtually excited and efficient decoherence time of the cavity is greatly prolonged. Compared to other protocols, this protocol is simpler and has a higher fidelity.

关键词： GHZ QED

Generation of Maximally Entangled States of Two Nonidentical Atoms in Cavity QED

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Communications in Theoretical Physics 2005年第1X期44卷 37-39页

作者： LIYu-Liang ZHOUZheng-Wei PANGChao-Yang GUOGuang-Can keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026China DepartmentofPhysics&ElectronicInformationEnginerring MinjiangUniversityFuzhou350108China//KeyLaboratoryofQuantumInformationUniversityofScienceandTechnologyofChinaHefei230026China

We have discussed the system which consists of two nonidentical two-level atoms trapped simultaneously in a large-detuned single-mode cavity field in this paper. The results show that it is possible to generate maximally entangled states for two nonidentical two-level atoms only if the cavity frequency and difference of two nonidentical atoms transition frequency are selected and the cavity-atom interacation time is controlled.

关键词： QED空穴有限电子去谱不恒等原子原子频率

Explicit Protocol for Deterministic Entanglement Concentration

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Chinese Physics Letters 2005年第7期22卷 1592-1595页

作者：顾永建高朋郭光灿 DepartmentofPhysics OceanUniversityofChinaQingdao266071 keylaboratoryofquantuminformation UniversityofScienceandTechnologyofChinaHefei230026

We present an explicit protocol for extraction of an EPR pair from two partially entangled pairs in a deterministic fashion via local operations and classical communication. This protocol is constituted by a local measurement described by a positive operator-valued measure (POVM), one-way classical communication, and a corresponding local unitary operation or a choice between the two pairs. We explicitly construct the required POVM by the analysis of the doubly stochastic matrix connecting the initial and the final states. Our scheme might be useful in future quantum communication.

关键词： LOCC POVM Deterministic