一个传送原子纠缠态的新方案

本文提出一个通过原子和腔场相互作用传送未知原子纠缠态的新方案,并且成功概率为100%.在这个方案里,我们主要利用两个原子用来接受被传送的原子纠缠态以及一个双模腔作为量子通道.由于腔场的两个模具有不同的频率和正交极化,因此这两个模能够被区分,并且处于腔场的不同区域.原子和腔场通过J-C哈密顿量发生共振相互作用,当原子和其中一个模相互作用时,另外一个模不受影响.该方案既不需要贝尔态测量,也不需要任何操作重构纠缠初态.这个方案也可以推广到传送N个原子的纠缠态.     

T-C模型中光场和原子以及原子与原子之间的纠缠演化

研究了T-C模型中的二能级原子与单模场以及两个二能级原子之间不同初态的纠缠演化.发现,它们之间的形成纠缠是周期演化的,不同初态纠缠演化的周期不同.在一种类W初态下两原子之间还出现所谓的纠缠猝灭现象. 关键词： T-C模型 纠缠度 纠缠猝死     

Implementing Entanglement Swapping and Generating Multiphoton Entanglement in Cavity QED

Based on the input-output relation of a one-sided cavity, we propose an experimental scheme to implement entanglement swapping with photons. In the ideal case, the successful probability of the scheme approaches unity. In addition, the protocol can be extended to establish multiphoton entanglement among distant users in a communication network.     

Entanglement evolution in an anisotropic two-qubit Heisenberg XYZ model with Dzyaloshinskii-Moriya interaction

This paper investigates the entanglement evolution of a two-qubit anisotropic Heisenberg XYZ chain in the presence of Dzyaloshinskii-Moriya interaction.The time evolution of the concurrence is studied for the initial pure entangled states cos θ |00 + sin θ |11 and cos |01 + sin |10 at zero temperature.The influences of Dzyaloshinskii-Moriya interaction D,anisotropic parameter and environment coupling strength γ on entanglement evolution are analysed in detail.It is found that the effect of noisy environment obviously suppresses the entanglement evolution,and the Dzyaloshinskii-Moriya interaction D acts on the time evolution of entanglement only when the initial state is cos |01 + sin |10.Finally,a formula of steady state concurrence is obtained,and it is shown that the stable concurrence,which is independent of different initial states and Dzyaloshinskii-Moriya interaction D,depends on the anisotropic parameter and the environment coupling strength γ.     

强度相关耦合双Jaynes-Cummings模型中的纠缠和量子失谐

研究强度相关耦合双Jaynes-Cummings模型中, 两运动原子初始处于最大纠缠态、光场初始处于单模热态时, 强度相关耦合、热光场平均光子数以及原子运动对两原子的纠缠和量子失谐的影响. 结果表明: 考虑强度相关耦合时, 纠缠和量子失谐均出现周期性地消失和回复现象, 并且, 回复以后的纠缠和量子失谐能达到初始值. 腔场温度的升高会加速纠缠和量子失谐的消失. 此外, 原子运动的场模结构参数对该模型中的纠缠和量子失谐影响很大, 其值选择合适时, 两个原子能够自始至终地保持纠缠或量子失谐状态. 关键词： 强度相关耦合 双Jaynes-Cummings模型 纠缠 量子失谐     

Entanglement dynamics between an isolated atom and a moving atom in the cavity

The entanglement dynamics between an isolated atom and a moving atom interacting with a cavity field is investigated. The results show that there appears sudden death of entanglement between the isolated atom and the moving atom and that the time of entanglement sudden death (ESD) is independent of the initial state of the system. It is interesting that the isolated atom can also entangle with a cavity field, though they do not interact with each other originally, which stems from the fact that the entanglement between the isolated atom and the moving atom may turn into the entanglement between the isolated atom and the cavity.     

含时旋转磁场中的两耦合粒子的纠缠演化(英文)

我们研究了含时旋转磁场中海森堡XXX模型下的双量子比特的动力学演化情况.基于此非自治系统的代数结构,我们用代数动力学方法求得了系统的精确解析解.在此基础上,进一步研究了在不同初态下系统的纠缠测度随时间的演化,发现纠缠测度由系统的初态的系数和耦合强度决定.     

费米环境中两个三能级原子系统的纠缠演化

利用负性纠缠度(negativity)研究了两个三能级原子系统在费米环境中的纠缠演化问题-结果表明,两个三能级原子系统的纠缠演化不仅依赖于系统和环境的相互作用强度,而且还依赖于系统所处的具体量子态-通过例子发现,系统和环境相互作用强度越大,纠缠衰减越快;对于纯态,仅当时间趋于无穷时纠缠才被完全破坏;对于混态,则在有限的时间内纠缠即被彻底破坏-通过一般的分析找到了一类免退相干的量子子空间-在这些子空间中,量子态不受环境的影响,故其纠缠不变-研究有助于理解费米环境造成的退相干对玻色系统纠缠的影响- 关键词： 费米环境 纠缠演化 两个三能级原子     

Entanglement evolution of a two-qubit system interacting with a quantum spin environment

We investigate the entanglement dynamics and decoherence of a two-qubit system under a quantum spin environment at finite temperature in the thermodynamics limit. For the case under study, we find different initial states will result in different entanglement evolution, what deserves mentioning here is that the state |Ψ=cosα|01+sinα|10 is most robust than other states when π/2<α<π, since the entanglement remains unchanged or increased under the spin environment. In addition, we also find the anisotropy parameter Δ can suppress the destruction of decoherence induced by the environment, and the undesirable entanglement sudden death arising from the process of entanglement evolution can be efficiently controlled by the inhomogeneous magnetic field ζ.     

Entanglement transfer via the Raman atom-cavity-field interaction

For the Raman interaction between an atom and a two-mode cavity field prepared in the state |01> or |10> , the atom and the field can be disentangled periodically. Such a property of Raman atom-field interaction allows the full entanglement transfer among many atoms and bimodal cavities. In the calculations, each atom is assumed to interact with its own cavity at a different time and so non-identical atoms can be treated conveniently. Entanglement sudden death is discussed too. Though atom-field interaction greatly changes the values of the concurrence for two atoms, configuration of the concurrence is almost not affected. When there is entanglement sudden death, atoms and cavities can still be entangled with one another. However, full entanglement transfer cannot be achieved for such systems with Raman atom-field interaction.     

利用交叉克尔非线性效应实现纠缠转移

提出了一种基于交叉克尔非线性效应的纠缠态转移方案.利用该方案可以将离散变量光场态之间的纠缠关系转移到连续变量光场态(相干态)上.通过适当设置初始相干态的振幅,该方案可以使转移后的纠缠相干态处于最大纠缠态. 关键词： 交叉克尔效应 纠缠转移 纠缠相干态     

Entanglement transfer via two arrays of coupled resonator waveguides

We propose a scheme for transferring entanglement through two independent arrays of coupled resonator waveguides,where a three-level atom is embedded in each resonator.We investigate the entanglement dynamics of the transferred state.The influence of initial states and applied lasers on the entanglement sudden death phenomenon is also discussed.Furthermore,we study the dynamics of pairwise quantum correlations measured by the quantum discord.     

Entanglement dynamics of a double two-photon Jaynes-Cummings model with Kerr-like medium

In this paper, the entanglement dynamics of a double two-photon Jaynes--Cummings model with Kerr-like medium is investigated. It is shown that initial entanglement has an interesting subsequent time evolution, including the so-called entanglement sudden death effect. It is also shown analytically that the Kerr-like medium can repress entanglement sudden death and enhance the degree of atom--atom entanglement. A more interesting fact is that the Kerr effect is more obvious when each of the two cavities with have the Kerr-like medium than only one of them with the Kerr-like medium.     

Entanglement transfer via two arrays of coupled resonator waveguides

We propose a scheme for transferring entanglement through two independent arrays of coupled resonator waveguides, where a three-level atom is embedded in each resonator. We investigate the entanglement dynamics of the transferred state. The influence of initial states and applied lasers on the entanglement sudden death phenomenon is also discussed. Furthermore, we study the dynamics of pairwise quantum correlations measured by the quantum discord.     

双光子Jaynes-Cummings模型中的纠缠演化和热纠缠态现象

文中利用共生纠缠度研究了双光子Jaynes-Cummings模型中原子与腔纠缠的时间演化和有限温度下系统热纠缠态.结果表明,腔场中原子与腔展现出周期性的纠缠演化过程,演化周期随原子与腔耦合强度的增大而减小;在有限温度下,系统的共生纠缠度随温度的升高而降低,当趋近临界温度时,系统纠缠现象消失,这一临界温度值与原子-腔耦合强度成正比.对于典型的实验数据,临界温度大约在～10-5 K数量级.     

Entanglement evolution of three-qubit mixed states in multipartite cavity—reservoir systems

We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state.For a composite system consisting of three cavities interacting with independent reservoirs,it is shown that the entanglement evolution is restricted by a set of monogamy relations.Furthermore,as quantified by the negativity,the entanglement dynamical property of the mixed entangled state of cavity photons is investigated.It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death(ESD).However,compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement,the ESD time of mixed states is later than that of the pure state.Finally,we discuss the entanglement distribution in the multipartite system,and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.     

Conditional Generation of Multiparticle Entanglement via Cavity QED

We propose a simple scheme to not only generate GHZ states and W states of the multiparticle but also form a new category of multiparticle entangled states by letting the A-type three-level atoms simultaneously interacting with a coherent cavity field followed by the selective measurements on the cavity mode. We investigate the influence of the cavity dissipation on the generated entangled state and discuss the experimental feasibility of our scheme. It is shown that the intensity of the coherent cavity field plays an instructive role in contribution to state preparation process while the cavity decay and the detuning between the atoms and cavity mode result in the deterioration of the generated entangled state.     

Entanglement in Three-Atom Tavis-Cummings Model Induced by a Thermal Field

The explicit form of the evolution operator for the three-atom Tavis-Cummings model is given. The atoms can be entangled through their interaction with a thermal field. The degree of entanglement depends on the mean photon number of the thermal field and the initial state of the atoms.     

A Position-Dependent Two-Atom Entanglement in Real-Time Cavity QED System

We study a special two-atom entanglement case in assumed cavity QED experiment in which only one atom effectively exchanges a single photon with a cavity mode. We compute two-atom entanglement under position-dependent atomic resonant dipole-dipole interaction （RDDI） for large interatomic separation limit. We show that the RDDI, even t, hat which is much smaller than the maximal atomic Rabi frequency, can induce distinct diatom entanglement. The peak entanglement reaches a maximum when RDDI strength can compare with the Rabi frequency of an atom.     

Entanglement and non-Markovianity of a multi-level atom decaying in a cavity

We present a paradigmatic method for exactly studying non-Markovian dynamics of a multi-level V-type atom interacting with a zero-temperature bosonic bath. Special attention is paid to the entanglement evolution and the dynamical nonMarkovianity of a three-level V-type atom. We find that the entanglement negativity decays faster and non-Markovianity is smaller in the resonance regions than those in the non-resonance regions. More importantly, the quantum interference between the dynamical non-Markovianities induced by different transition channels is manifested, and the frequency domains for constructive and destructive interferences are found.