Generation of a χ-type four-atom entangled state

This paper proposes a scheme to generate a new χ-type four-atom entangled state for the first time by using linear optics elements, four one-sided cavities (one three-level atom) and a conventional photon detector. The linear optical elements and conventional photon detector are simple and accessible in experiments, which makes the scheme more feasible with current technology. In addition, the state |χ⁰⁰₃₂₁₄ with probability 1 can be generated as long as there is no photon loss.     

The influences of dipole--dipole interaction and detuning on the sudden death of entanglement between two atoms in the Tavis--Cummings model

The influences of dipole--dipole interaction and detuning on the entanglement between two atoms with different initial tripartite entangled W-like states in the Tavis--Cummings model have been investigated by means of Wootters' concurrence, respectively. The results show that the entanglement between the two atoms can be enhanced via appropriately tuning the strength of dipole--dipole interaction of two atoms or the detunings between atom and cavity, and the so-called sudden death effect can be weakened simultaneously.     

与非等同双原子相互作用下光场的量子特性

研究了具有不同偶极矩的两个原子与双模压缩真空场相互作用系统中光场的量子特性.讨论了两个原子与双模压缩真空场的相对耦合常数(R=g1/g2)和光场的初始压缩因子r对光场的压缩效应和光子的聚束与反聚束效应的影响.数值计算结果表明,光场量子涨落的震荡幅度、最大压缩深度、压缩时间及二阶相干度的震荡振幅与光场的初始压缩因子r的大小有关.两原子与双模光场的相对耦合常数R影响着光场量子涨落和二阶相干度的震荡规律,因而也影响着压缩时间、光场处于非经典态的时间及光子的反聚束程度,但对光场的压缩深度无明显影响.     

Complete hyperentangled state analysis and generation of multi-particle entanglement based on charge detection

We propose the schemes for implementing hyperentangled state analysis and generating four-electron high entan-gled states （including cluster state, ｜X） state, and symmetric Dicke state） based on the charge detection of free electrons. These schemes are deterministic and rely only on charge detection and single-spin rotations. This method, which uses noninteracting electrons, is not only efficient but also saves on quantum resources.     

A realizable multi-bit dense coding scheme with an Einstein—Podolsky—Rosen channel

We propose a multi-bit dense coding scheme by using only an Einstein-Podolsky-Rosen(EPR) channel and assistant qubits.It is shown that no matter how many classical bits there are,the quantum channel is always a Bell state.The present dense coding process can also prepare non-local multi-particle Greenberger-Horne-Zeilinger(GHZ) states at one of the participants.The quantum circuits for this dense coding process are constructed,the deterministic implementation method in an optical system based on the cross-Kerr nonlinearities is shown.     

Quantum-Dot Spin-Based Secret Sharing in an Optical Microcavity

Two schemes of quantum secret sharing are proposed via single electron spin confined in charged QDs inside a single-sided microcavity and a double-sided microcavity, respectively. Both schemes rely on coherent photonspin interaction. The two schemes axe both deterministic and can be extended to multipartite secret sharing.     

Pairwise thermal entanglement in a three-qubit Heisenberg XX model with a nonuniform magnetic field and Dzyaloshinski-- Moriya interaction

Pairwise thermal entanglement in a three-qubit Heisenberg XX model is investigated when a nonuniform magnetic field and the Dzyaloshinski-Moriya interaction are included. We find that the nonuniform magnetic field and Dzyaloshinski-Moriya interaction are the more efficient control parameters for the increase of entanglement and critical temperature. For both the nearest neighbour sites and the next nearest neighbour sites, the magnetic field can induce entanglement to a certain extent and the Dzyaloshinski-Moriya interaction can enhance the entanglement to a stable value. The steady value of the nearest neighbour site entanglement C 12 is larger than the next nearest neighbour site entanglement C 13 . An interesting phenomenon is that the entanglement curve of C 12 appears a peak value when the Dzyaloshinski-Moriya interaction is considered in a nonuniform magnetic field.     

原子运动对与V型三能级原子作用的双模光场压缩效应的影响

应用全量子理论和数值分析的方法研究了在双模光场与运动的V型三能级原子相互作用过程中，原子运动对双模场压缩的影响。结果表明，当初始光场处于非关联双模相干态时，只有光场的第一正交分量被压缩，压缩程度随着原子运动与场模结构参数的增大而增大。另一方面，当初始光场处于双模压缩真空态时，主要是光场的第二正交分量被压缩，并且通过适当选择原子运动与场模结构参数，能够获得稳定的压缩光。     

Time-bin-encoding-based remote states generation of nitrogen-vacancy centers through noisy channels

We design proposals to generate a remote Greenberger-Horne-Zeilinger(GHZ) state and a W state of nitrogenvacancy(NV) centers coupled to microtoroidal resonators(MTRs) through noisy channels by utilizing time-bin encoding processes and fast-optical-switch-based polarization rotation operations.The polarization and phase noise induced by noisy channels generally affect the time of state generation but not its success probability and fidelity.Besides,the above proposals can be generalized to n-qubit between two or among n remote nodes with success probability unity under ideal conditions.Furthennore,the proposals are robust for regular noise-changeable channels for the n-node case.This method is also useful in other remote quantum information processing tasks through noisy channels.     

辫子Hopf代数的积分

本文引进了无限维辫子Hopf代数日的忠实拟对偶H~d和严格拟对偶H~(d′)．证明了每个严格拟对偶H~(d′)是一个H-Hopf模．发现了H~d的极大有理H~d-子模H~(drat)与积分的关系,即：H~(drat)≌∫_(H~d)~l■H．给出了在Yetter-Drinfeld范畴(_B~ByD,C)中的辫子Hopf代数的积分的存在性和唯—性．