失谐对腔量子电动力学系统中纠缠特性的影响

采用Negativity度量两子系统间的纠缠,研究了两个全同二能级原子与腔相互作用系统中的量子纠缠。考虑原子与腔场失谐相互作用,并且原子间存在偶极相互作用的情况。利用数值计算方法,讨论了失谐量和偶极相互作用强度变化对量子纠缠的影响。研究结果表明:随失谐量增大和偶极相互作用强度增大,两原子间纠缠增强。另一方面,随失谐量逐渐增大,两原子间纠缠呈现出从不规则振荡向准周期性振荡转变。随偶极相互作用强度增大,原子间纠缠振荡频率加快。     

开放系统中量子比特与环境纠缠特性的研究

研究了由两个二能级原子与一个零温热库所组成的系统的纠缠动力学过程.考虑原子间的偶偶相互作用及原子与热库之间的失谐,对于初始原子间有纠缠与无纠缠两种情况,研究了不同的参数条件对系统纠缠的影响.计算了两原子间、原子与热库之间的对纠缠以及整个系统的三体纠缠,结果表明在两原子初始处于最大纠缠态时,所有的对纠缠最终都趋于零.增大原子间的偶偶相互作用强度,原子与热库之间的纠缠会被减弱,而原子间的纠缠以及系统三体间的纠缠被增强.增大原子与热库之间的失谐量,两原子之间的纠缠会增大,原子与热库以及三体间的纠缠会减弱.     

共同环境中三原子间纠缠演化特性研究

研究了三个二能级原子与共同热库发生相互作用的系统纠缠动力学演化. 采用三体负本征值来描述系统间纠缠, 通过数值计算分析了初始状态和原子间偶极-偶极相互作用对系统间纠缠演化的影响. 结果表明, 初始状态的原子相位可以控制量子干涉现象; 长时间演化下原子的激发态布居出现俘获现象; 通过调节偶极-偶极相互作用强度, 可以提升三原子间纠缠.     

Tavis-Cummings模型中两纠缠原子纠缠的演化特性

研究了两个纠缠的两能级原子与单模粒子数场进行相互作用系统中两原子的纠缠演化.结果表明：两个原子之间的纠缠呈现出周期性的演化特性，初始两原子的状态、原子之间的偶极相互作用和粒子数场对腔中两个原子的纠缠有着显著的影响.发现适当选择原子的初态，两原子会永远处于最大纠缠态. 关键词： 量子纠缠 偶极-偶极相互作用 部分转置矩阵负本征值 纠缠原子     

级联环境下双原子的纠缠动力学

文献Phys.Rev.A 90,042108(2014)提出了一种级联环境模型,即单量子系统与光学腔作用,而腔又级联着一个有结构的零温玻色热库。本文在此基础上,研究两个二能级原子在该级联环境下的纠缠动力学,考察原子与腔场的耦合强度、原子间的偶极-偶极相互作用、热库的谱宽度、腔场与库间的失谐对原子间纠缠以及两原子与腔组成的三体纠缠动力学的影响。结果表明,在一定条件下两原子间的二体纠缠和原子-腔的三体纠缠在长时极限下都趋于稳定值,且随着偶极-偶极相互作用增加而增大,而无论腔场与热库耦合强弱,失谐量的增加都可以抑制纠缠的衰减。     

非旋波近似下两纠缠原子的纠缠特性

采用了相干态正交化法研究了耦合强度以及偶极相互作用对Tavis-Cummings模型中两原子的纠缠的影响.与旋波近似比较发现,在弱耦合强度下,非旋波近似下两原子间的纠缠与旋波近似下的结果符合得很好,在强耦合区,原子之间的纠缠出现了突然死亡现象.研究同时发现耦合强度越大,原子间处于可分离态的时间越长,表明了原子间处于退纠缠的时间的长短是依赖于原子-光场的耦合强度的.而考虑了偶极相互作用时,随着偶极-偶极相互作用的加强,原子间的纠缠也将被加强.     

内禀退相干下Tavis-Cummings模型中原子的纠缠演化与贝尔不等式破坏

通过求解系统的Milburn方程，研究了两个二能级原子和单模场相互作用系统中原子间纠缠和贝尔不等式破坏随时间的演化特性，讨论了偶极相互作用、场与原子的失谐量对纠缠度以及贝尔不等式破坏的影响.结果表明：原子间偶极-偶极相互作用对纠缠度和贝尔不等式破坏有显著影响，失谐量增大会使两原子的纠缠度和贝尔不等式破坏变大，并且两原子所能达到稳定的纠缠受偶极相互作用系数与失谐量两者之差的影响.同时还发现两原子的纠缠与贝尔不等式破坏并不是单调的函数关系，很小的纠缠也可以产生贝尔不等式破坏. 关键词： Milburn理论 偶极-偶极相互作用 失谐量 贝尔不等式破坏     

共振和非共振情况下非简并双光子Tavis-Cummings模型中原子与原子之间的纠缠演化

针对共振和非共振情况讨论了非简并双光子Tavis-Cummings(T-C)模型中原子与原子之间的纠缠演化,得到纠缠度的解析表达式.基于两类型不同的初态,详细分析了光场本征频率、原子跃迁频率以及原子与原子间偶极相互作用对纠缠的影响,并比较了共振和非共振情况下的纠缠演化行为.     

非旋波近似下两纠缠原子的纠缠特性

采用了相干态正交化法研究了耦合强度以及偶极相互作用对Tavis-Cummings模型中两原子的纠缠的影响.与旋波近似比较发现,在弱耦合强度下,非旋波近似下两原子间的纠缠与旋波近似下的结果符合得很好,在强耦合区,原子之间的纠缠出现了突然死亡现象.研究同时发现耦合强度越大,原子间处于可分离态的时间越长,表明了原子间处于退纠缠的时间的长短是依赖于原子-光场的耦合强度的.而考虑了偶极相互作用时,随着偶极-偶极相互作用的加强,原子间的纠缠也将被加强.     

用腔场QED技术实现量子信息转移

提出了一种量子信息转移方案,它是基于两个耦合的二能级原子同时与单模腔场发生大失谐相互作用实现的.通过控制腔场与双原子的相互作用时间,量子信息可以从一个原子转移到另一个原子,或从单模腔场转移到双原子纠缠态上,而包含在欲转移量子态上的信息被完全檫除. 关键词： 大失谐Jaynes Cummings模型 量子信息转移 偶极 偶极相互作用     

Tavis-Cummings模型中的几何量子失协特性

采用几何量子失协的计算方法,通过改变两原子初始状态、腔内光子数和偶极-偶极相互作用强度,研究了Tavis-Cummings模型中的几何量子失协特性.结果表明:几何量子失协都是随时间周期性振荡的,选取适当的初态可以使两原子一直保持失协状态,增加腔内光子数和偶极相互作用对几何量子失协有积极的影响.     

Quantum correlation dynamics of three non-coupled two-level atoms in different reservoirs

Time evolution dynamics of three non-coupled two-level atoms independently interacting with their reservoirs is solved exactly by considering a damping Lorentzian spectral density.For three atoms initially prepared in Greenberger-Horne-Zeilinger-type state,quantum correlation dynamics in a Markovian reservoir is compared with that in a nonMarkovian reservoir.By increasing detuning quantity in the non-Markovian reservoir,three-atom correlation dynamics measured by negative eigenvalue presents a trapping phenomenon which provides long-time quantum entanglement.Then we compare the correlation dynamics of three atoms with that of two atoms,measured by quantum entanglement and quantum discord for an initial robuster-entangled type state.The result further confirms that quantum discord is indeed different from quantum entanglement in identifying quantum correlation of many bodies.     

Quantum correlation dynamics of two qubits in independent reservoirs with initial system-reservoir correlations

The dynamics of entanglement and quantum discord(QD) between two two-level atoms interacting with two dissipative coupled cavities in the presence of initial atom-cavity correlations is investigated. In comparison with the result of the initial factorized state, we show that the initial state contained quantum correlation of atom-cavity is most robust against the dissipative environment, and the initial atom-cavity correlations, especially the quantum correlation, play a constructive role in the generation of atomic entanglement and QD.Simultaneously, the comparison between Markovian and non-Markovian dynamics, and the influences of inter-cavity hopping rate are also taken into account and analyzed.     

Collapse–revival of quantum discord and entanglement

In this paper the correlations dynamics of two atoms in the case of a micromaser-type system is investigated. Our results predict certain quasi-periodic collapse and revival phenomena for quantum discord and entanglement when the field is in Fock state and the two atoms are initially in maximally mixed state, which is a special separable state. Our calculations also show that the oscillations of the time evolution of both quantum discord and entanglement are almost in phase and they both have similar evolution behavior in some time range. The fact reveals the consistency of quantum discord and entanglement in some dynamical aspects.     

Enhancement of stationary state quantum discord in Tavis-Cummings model by nonlinear Kerr-like medium

We investigate the influence of nonlinear Kerr-like medium and dipole-dipole interaction on the dynamics of quantum discord in Tavis-Cummings model with phase decoherence. We show that in the resonance case (i) atom-field quantum discord rapidly decays with phase decoherence and doesn't exist the stationary state quantum discord, but the stationary state quantum discord appears if we choose the suitable values of Kerr coefficient χ and dipole-dipole interaction Ω, (ii) the quantum discord of two atoms survives in the stationary state and the amount of stationary state quantum discord could be improved by adjusting the values of χ and Ω. In the non-resonance case, the arbitrary bipartite quantum discord of the system could not be completely destroyed by the phase decoherence and can be improved by applying nonlinear Kerr-like medium and dipole-dipole interaction.     

Quantum Discord of two Coupled Qubits with Initial System-reservoir Correlation

Recently, the effect of initial qubit-reservoir correlation for two qubits in a common reservoir on the entanglement dynamics has been studied by Yan and Xia (Acta Sinica Quantum Optica 20, 16 2014). We extend their results and investigate how the initial qubit-reservoir correlation and dipole-dipole interaction between two qubits effect on dynamics of quantum discord in Markovian and non-Markovian regimes, respectively. The results show that in general, the larger initial qubit-reservoir correlation and dipole-dipole interaction can retard the decay of quantum discord. Besides, a combination of relatively strong dipole-dipole interaction and non-Markovian effect can efficiently protect quantum discord. Finally,thecomparisonbetweenevolutionsofquantumdiscordandentanglementisalsoconsidered.     

Correlation Dynamics of Three-Qubit System Under a Classical Dephasing Environment

By starting from the stochastic Hamiltonian of the three correlated spins and modeling their frequency fluctuations as caused by dephasing noisy environments described by Ornstein-Uhlenbeck (OU) processes, we study the dynamics of quantum correlations, including entanglement and quantum discord. Of course, in this article, we use two definitions for the quantum discord (global quantum discord and quantum dissension). We prepared initially our open system with the Greenberger-Horne-Zeilinger (GHZ) and W states and present the exact solutions for evolution dynamics of entanglement and quantum discord between three spins under both Markovian and non-Markovian regime of this classical noise. By comparison the dynamics of entanglement with that of quantum discord we find that entanglement can be more robust than quantum discord against this noise. It is shown that by considering non-Markovian extensions the survival time of correlations prolong. Also, we compare the results of two definitions of the quantum discord and show that the quantum dissension is equal to the global quantum discord for GHZ state, but they are unequal for the W state.     

Steady state quantum discord for circularly accelerated atoms

We study, in the framework of open quantum systems, the dynamics of quantum entanglement and quantum discord of two mutually independent circularly accelerated two-level atoms in interaction with a bath of fluctuating massless scalar fields in the Minkowski vacuum. We assume that the two atoms rotate synchronically with their separation perpendicular to the rotating plane. The time evolution of the quantum entanglement and quantum discord of the two-atom system is investigated. For a maximally entangled initial state, the entanglement measured by concurrence diminishes to zero within a finite time, while the quantum discord can either decrease monotonically to an asymptotic value or diminish to zero at first and then followed by a revival depending on whether the initial state is antisymmetric or symmetric. When both of the two atoms are initially excited, the generation of quantum entanglement shows a delayed feature, while quantum discord is created immediately. Remarkably, the quantum discord for such a circularly accelerated two-atom system takes a nonvanishing value in the steady state, and this is distinct from what happens in both the linear acceleration case and the case of static atoms immersed in a thermal bath.     

量子关联与原子间相互作用距离关系的研究

本文将两个二能级原子注入一个腔中,用共生纠缠的方法来度量两原子之间的纠缠并推出它们之间的量子失协,还给出了原子与环境之间的共生纠缠与量子失协的计算公式,讨论了原子自发衰变率的变化对量子纠缠及失协的影响,及不同的初始状态情况下,纠缠及失协随原子距离的演化情况。结果表明：原子自发衰变率减小,原子与环境之间的量子纠缠及失协增加;选择不同的初态,可以控制原子间出现纠缠死亡的现象或量子失协为零的状态。