Quantum Entanglement Dynamics of Two Atoms in Two Coupled Cavities

Quantum entanglement dynamics for two atoms trapped in two coupled cavities is investigated.Numerical results show that the present of the two atomic excitations is mainly accounted for the entanglement-sudden-death(ESD) effect with the two cavities initially in the vacuum.The entanglement can also be controlled by the hopping rate and the imbalances between the two atom-cavity coupling rates.     

类W态原子与三耦合腔系统作用中的量子失协

研究了三个全同二能级原子与三耦合腔相互作用物理模型中两原子间的量子失协.腔与腔之间通过光纤耦合,考虑原子与腔模之间的共振作用,采用几何量子失协来度量两原子间的量子关联,数值计算了系统中两原子间的几何量子失协,给出了其演化曲线.讨论了光纤模与腔模间的耦合强度变化对几何量子失协的影响.结果表明:随光纤模与腔模间的耦合强度增大,两原子间的几何量子失协增大,即两原子间量子关联增强.     

The Dynamics of Quantum Correlations Between Two Atoms in Two Coupled Cavities

The dynamics of the quantum correlation between two atoms in two single-mode cavities is studied. For the initial Bell state |Ψ ⁺〉, the quantum consonance is equal to the entanglement, and larger than quantum discord. For the initial Bell state |Φ ⁺〉, the quantum consonance is larger than entanglement, but not larger than quantum discord all the time. As the increase of the cavity-cavity coupling strength, the evolution period of quantum correlation becomes smaller. Consonance is not smooth at some points while cavities are coupled with each other.     

Entanglement and Quantum Discord Dynamics of Two Atoms in a Broadband Squeezed Vacuum Bath

We study the dynamics of entanglement and quantum discord between two two-level atoms that interact with a common squeezed reservoir. It is shown that the degree of entanglement and quantum discord are very sensitive to the degree of two-photon correlation for large values of the mean photon number. The squeezed vacuum environment can drive the system to a stationary state with high entanglement and quantum discord for certain X-type states. Furthermore, sudden change happens to the dynamics of quantum discord while the entanglement is remained almost unchanged.     

双光子过程原子与耦合腔相互作用中的量子失协

研究原子与耦合腔相互作用系统,考虑每个腔囚禁一个二能级原子,原子与腔场发生共振相互作用,腔场也相互耦合的情况;采用量子失协几何度量方法—几何量子失协,来度量两个子系统间的量子失协.利用数值计算方法给出了量子失协的演化曲线,讨论了腔场间耦合系数变化对量子失协的影响.研究结果表明:随腔场间耦合系数增大,两原子间量子失协增大,而原子与腔场间或两腔场间的量子失协却减小.     

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

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.     

Influences of Detuning on Geometrical Quantum Discord in Coupled Cavities System

Geometrical quantum discord (GQD) is adopted to quantify the degree of correlation between two subsystems. We consider the situation that two two-level atoms are separately trapped in coupled single-mode cavities, and each atom non-resonantly interacts with cavity via a one-photon hopping. GQD dynamic between atoms and that between cavities are studied. The influences of detuning on GQD dynamics are discussed. The results obtained by the numerical method show that GQD between atoms is strengthened with the increase of the detuning. Contrarily, GQD between cavities is weakened with the increase of the detuning.     

Geometrical Quantum Discord in the Coupled Cavities System with Tetrahedral Structure

In this paper we consider the situation that four identical two-level atoms are separately trapped in four single-mode optical cavities, which are placed at the vertices of a tetrahedron and coupled by six fibers. Each atom resonantly interacts with cavity via a one-photon hopping. The evolution of the state vector of the system is given by solving the schrödinger equation when the total excitation number of the system equals one. The geometrical quantum discords between atoms and between cavities are investigated. The effects of cavity-fiber coupling coefficient on the geometrical quantum discords between atoms and between cavities are discussed. The results obtained using the numerical method indicate that the geometrical quantum discords between atoms and between cavities are all weakened with increase of cavity-fiber coupling coefficient.

     

有心结构耦合腔系统中的几何量子失谐（英文）

引入了由N+1个单模腔构成的有心结构耦合腔物理模型.其中,中心腔起耦合器作用,其余N个腔通过N条光纤与中心腔耦合,并且每个腔囚禁1个二能级原子.在系统激发数等于1的情况下,给出了系统态矢的演化规律,研究了两原子间和两腔场间的几何量子失谐.通过数值计算,讨论了耦合腔数目和原子与腔场间耦合强度对几何量子失谐的影响.研究结果表明:随着腔数目的增加两原子间和两腔场间的几何量子失谐都减弱;随着原子与腔场间耦合系数增大,两原子间几何量子失谐减弱,但两腔场间几何量子失谐却加强.     

Quantum Entanglement Dynamics of Two Atoms in Quantum Light Sources

Quantum entanglement dynamics of two Tavis-Cummings atoms interacting with the quantum light sources in a cavity is investigated. The results show the phenomenon that the concurrence disappears abruptly in a finite time, which depends on the initial atomic states and the properties of squeezed states. We find that there are two decoherence-free states in squeezed vacuum fields: one is the singlet state, and the other entangled state is the state
that combines both excited states and ground states with a relative phase being equal to the phase of the squeezed state.     

The Entanglement Properties Induced by Atoms in Two Separate Cavities Connected by an Optical Fiber

We study the entanglement evolution between two atoms, which are initially entangled with a third atom and trapped in two separated cavities coupled by an optical fiber. We also investigate the temporal evolution in the entanglement between the atom and the local cavity mode. The influence of the state-selective measurement on the atom outside the cavities and the influence of cavity-fiber coupling coefficient on the entanglement are discussed. The results show that the entanglement can be strengthened through the state-selective measurement on the atom outside the cavities. We also find that, by increasing the cavity-fiber coupling coefficient, the atom-atom entanglement is strengthened, but the atom-cavity entanglement is weakened.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

等距离光纤耦合腔系统中的三体纠缠特性

考虑3个单模腔处于等边三角形的3个顶点,腔与腔之间通过光纤耦合,并且每个腔囚禁一个二能级原子的情况,研究了该系统中3个原子间和3个腔模间的三体纠缠特性.考虑系统激发数等于1的情况下,给出了系统态矢的演化规律;采用三体负本征值Negativity度量三体纠缠,通过数值计算给出了3个原子间和3个腔模间的三体纠缠演化曲线;讨论了腔模与光纤模间的耦合强度变化对纠缠特性的影响.研究结果表明:原子间和腔模间的三体纠缠量均呈现不规则振荡;随着腔模与光纤模间耦合系数增大,振荡频率增大,而原子间和腔模间的三体纠缠均减弱.     

Quantum Discord Dynamics of Three Qubits in Non-Markovian Environments

We investigate the dynamics of palrwise quantum discord （QD） for a mixed three-qubit W-type state in three independent non-Markovian reservoirs at zero temperature, each of which is modeled by a leaky cavity with Lorentzian spectral density. The influence of the environment＇s amount of non-Markovianity, the detuning between the qubit frequency and the cavity centre frequency, and the purity of the initial state on the QD dynamics are analyzed in detail. It is found that in the non-Maxkovian regime the system-reservoir interactions induce QD revivals and oscillations no matter whether the detuning is zero or not. Moreover, QD can be preserved for a long time if the non-Markovian condition and the detuning condition are satisfied simultaneously.     

Dynamics of Quantum Discord of Two-Qubit Coupled with a Vacuum Cavity

The dynamical behaviors of quantum discord between two atoms coupled with a vacuum cavity are investigated. If the two qubits are initially prepared in two extended Werner-like states, the quantum discord and entanglement can be numerically calculated. There are remarkable differences between the time evolutions of the quantum discord and entanglement under the same conditions. These results imply that quantum discord is not zero for some unentangled states and in some regions entanglement can disappear completely. A large amount of quantum discord exists between the two-qubit. Thus, the quantum discord is more robust than entanglement for the quantum system exposed to the environment. The quantum discord shows sudden change and its existence depends on the initial state of the system. This property of quantum discord may have important implications for experimental characterization of quantum phase transitions.     

远距离三原子量子纠缠特性与其应用

三原子分别被束缚在用光纤环形连接单侧泄漏微光学腔场中,在微腔中输入激光驱动场和施加局域激光场,利用输入-输出技术及绝热近似理论,推导出一维Ising链模型的有效哈密顿量,该哈密顿量表明该系统会诱导出三原子中的任意两原子纠缠及三原子纠缠,用伴随数(concurrence)度量两原子纠缠,用内禀纠缠度量三原子纠缠,通过数值计算,给出两原子和三原子纠缠随时间演化曲线,通过适当调控激光驱动场和局域激光场,在远距离三原子中任意两原子实现未知量子态的隐形传送。