Non-Markovian Effects on Entanglement Dynamics of Three Qubits

We investigate entanglement dynamics of three independent qubits each locally interacting with a zerotemperature non-Markovian reservoir. The effects of environment＇s amount of non-Markovianity or parameters in initial states on the three-qubit entanglement dynamics are presented in detail. It is found that the entanglement of such a system revives after a finite dark period when a proper degree of non-Markovian is present. A deep comparison to that in two-qubit system is also made.     

Bipartite Entanglement Dynamics in Three Qubits System withDzyaloshinskii-Moriya Interaction

We investigate the bipartite entanglement dynamics of the systemcomposed by three qubits A, B, and C. There is no interaction betweenA and B, and that of C and B is Dzyaloshinskii-Moriya (DM) spin-orbit interaction. We find that the purity of qubits A and B and the initial state of the qubit C are the two effective parameters to control the entanglement dynamics of the bipartite subsystems. This study sheds some lights on the control of quantum entanglement, which would be helpful for quantum information processing.     

Bipartite Entanglement Dynamics in Three Qubits System with Dzyaloshinskii-Moriya Interaction

We investigate the bipartite entanglement dynamics of the system composed by three qubits A, B, and C. There is no interaction between A and B, and that of C and B is Dzyaloshinskii-Moriya （DM） spin-orbit interaction. We find that the purity of qubits A and B and the initial state of the qubit C are the two effective parameters to control the entanglement dynamics of the bipartite subsystems. This study sheds some lights on the control of quantum entanglement, which would be helpful for quantum information processing.     

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.     

Entanglement Dynamics of Three Qubits in the Non-Markovian Environments

We consider the entanglement dynamics of three two-level atoms interacting with independent structured non-Markovian reservoirs. The atoms are initially prepared in a mixed multipartite Greenberger—Horne—Zeilinger （GHZ）-type state. Based on the purity and non-Markovian reservoirs, we show that the reservoirs＇ entanglement can exhibit not only multipartite entanglement sudden birth but also entanglement sudden death, and the revival of atom entanglement is not always accompanied by the disentanglement of reservoirs. Meanwhile, we derive the quantitative criteria for multipartite revival and death phenomena and find multipartite entanglement sudden death and entanglement sudden birth simultaneous apparition time is independent of the initial three-qubit state.     

Entanglement Dynamics of Two-Qubit System in Different Types of Noisy Channels

In this paper, we study entanglement dynamics of a two-qubit extended Werner-like state locally, interacting with independent noisy channels, i.e., amplitude damping, phase damping, and depolarizing channels. We show that the purity of initial entangled state has direct impacts on the entanglement robustness in each noisy channel. That is, if the initial entangled state is prepared in mixed instead of pure form, the state may exhibit entanglement sudden death （ESD） and/or be decreased for the critical probability at which the entanglement disappear.     

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.     

Entanglement Dynamics of Three Superconducting Charge Qubits Coupled to a Cavity

We investigate the entanglement dynamics of a quantum system consisting of three superconducting charge qubits (SCQs) interacting with a microwave field. For separable and entangled states of the SCQs, the evolutions are studied under various photon numbers of cavity field. The results show that the amplitude and period of the bipartite entanglement square concurrences can be controlled by the choice of initial states of SCQs and photon numberof cavity field, respectively. This simple model of a quantum register allows us to understand the dynamic process of the quantum storage of information carried by charge qubit.     

Dynamics of Quantum Entanglement in Reservoir with Memory Effects

The non-Markovian dynamics of quantum entanglement is studied by the Shabani-Lidar master equation when one of entangled quantum systems is coupled to a local reservoir with memory effects.The completely positive reduced dynamical map can be constructed in the Kraus representation.Quantum entanglement decays more slowly in the non-Markovian environment.The decoherence time for quantum entanglement can be markedly increased with the change of the memory kernel.It is found out that the entanglement sudden death between quantum systems and entanglement sudden birth between the system and reservoir occur at different instants.     

Entanglement for Two-Qubit Extended Werner-Like States: Effect of Non-Markovian Environments

We investigate the sudden birth and sudden death of entanglement of two qubits interacting with uncorrelated structured reservoirs. The system is initially prepared in two-qubit extended Werner-like state. We work out the dependence of the entanglement dynamics on both non-Markovian environments and the purity of initial state, and show that non-Markovian environments and the purity can control the time of the two-qubit entanglement sudden death and the reservoirs' entanglement sudden birth.Furthermore, under the conditions of different purity and initial entanglement, the revival of qubits' entanglement can manifest before, simultaneously or even after the disentanglement of their corresponding reservoirs.     

非马尔科夫环境下耦合超导量子系统纠缠演化的数值研究

基于耦合超导量子比特系统模型下,在非马尔科夫环境中利用共生纠缠的方法分析了耦合系统纠缠的产生及其动力学的演化。研究了不同初始纠缠态下的纠缠猝死(ESD)和纠缠再生(ESB)现象;主要分析了系统耦合强度、库的截止频率与系统的振荡频率间的比值、温度和约瑟夫森能级差对纠缠演化的影响。结果表明:系统纠缠取决于初始纠缠态和系统的耦合强度J,并且通过调节以上非马尔科夫环境的相干参数可以延长解纠缠时间来确保量子计算过程中的应用和量子信息的实现。     

两个V型三能级原子系统的纠缠突然死亡与复苏

研究了在真空辐射场作用下,两个V型三能级原子系统的纠缠随时间的演化特性.发现当两原子间距较远,自发辐射会导致纠缠退化,甚至导致纠缠突然死亡,而原子激发态衰变的速率会影响纠缠死亡的时间;当两原子间距非常小,由于原子间的合作效应,死亡后的纠缠会在一段时间后复苏,初始的纠缠和复苏的纠缠由不同的原因引起.     

Three-Qubit Entanglement Sudden Death

We study entanglement dynamics of three-qubit system via negativity. Three atoms A, B, and C interact isolatedly with their own Jaynes-Cummings cavities a, b, and c. Aa system is prepared entangled with Bb and Cc, however, their mutual isolations forbid Aa interacting with system Bb and Cc. It is the same for system Bb and Cc. We show entanglement evolution of different three-qubit systems ABC, abc, Abc, and aBC and find entanglement sudden death effect.     

类克尔介质光腔中原子的纠缠动力学研究

初始处于纠缠的原子与附加类克尔介质的光腔相互作用,运用共生纠缠的度量方法对原子间的纠缠演化动力学进行研究,分析了腔场粒子数、介质非线性效应及原子与腔场的失谐量对纠缠演化的影响,发现处于腔场真空态下原子间的纠缠作周期性震荡演化,而处在腔场粒子数态下的原子在演化过程中发生纠缠突然死亡现象;在非线性克尔介质作用下,处于腔场粒子数较小范围内(n≤5)的原子间也会产生纠缠突然死亡现象;但随着腔场粒子数的增加纠缠突然死亡现象消失而且一定程度上可以达到纠缠初始值;当腔场处于任意粒子数态时,由于非线性效应的影响,均可抑制纠缠突然死亡现象的发生;当腔场在没有类克尔介质作用时,原子与腔场间的失谐量同样可以避免纠缠突然死亡现象的发生.     

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.     

Control of Sudden Death of Entanglement by Transient Effects

We investigate the properties of entanglement between an isolated atom and a Jaynes-Cummings atom in the presence of transient effects. These effects are due to the modulation of the atom-field coupling whose explicit time-dependence is considered for the case of the linear sweep. We show that the sudden death of entanglement can be controlled by the transient effects. These effects can suppress the sudden death of entanglement in time.     

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     

两Jaynes-Cummings原子间的纠缠动力学和转移特性

采用两种不同的纠缠度量方法(并发度和负值度),研究了两Jaynes-Cummings原子之间的纠缠演化以及各子系统之间的纠缠转移,分析了两原子之间初始纠缠度对纠缠的影响.结果表明纠缠的幅值依赖于初始纠缠度,而解纠缠时间长度与初始纠缠度无关.制备了两个腔场之间的最大纠缠态,数值分析显示两原子之间的初始纠缠流入了其它各个子系统,导致演化过程中的纠缠突然死亡和纠缠突然产生现象.     

Entanglement Dynamics of Strongly-AC-Driven Superconducting Qubits in Circuit QED

We study the entanglement dynamics between two strongly-AC-driven superconducting charge qubits coupled collectively to a zero temperature, dissipative resonator and find an unusual feather that the competing of creation and annihilation of entanglement can lead to entanglement increasing, sudden death and revival. We also calculate the dependence of the death time on the initial state of the system.