Effects of Pure Dzyaloshinskii-Moriya Interaction with Magnetic Field on Entanglement in Intrinsic Decoherence

We investigate the effects of pure Dzyaloshinskii Moriya （DM） interaction with magnetic field on entanglement in intrinsic decoherence, assuming that the system is initially in four Bell states ｜φ±〉 = （｜00） ± ｜11〉）/√2 and ｜ψ±〉 = （｜01） ±｜10〉）/√2, respectively. It is found that if the system is initially in the state p1（0） = ｜φ＋〉〈φ＋1, the entanglement can obtain its maximum when the DM interaction vector D is in the plane of XOZ and magnetic field B = By with the infinite time t, moreover the entanglement is independent of By and t when By is perpendicular to D. In addition, we obtain similar results when the system is initially in the states p2（0） = ｜φ-〉〈φ-｜ or p3 （0） = ｜ψ＋〉〈ψ＋1. However, we find that if the system is initially in the state P4 （0） = ｜ψ-〉〈ψ-l, the entanglement can obtain its maximum for infinite t, when the DM vector is in the plane ofYOZ, XOZ, or XOY, with the magnetic field parallel to X, Y, or Z axis, respectively. Moreover, when the axial B is perpendicular to D for the initial state p4（O）, the negativity oscillates with time t and reaches a stable value, the larger the value of B is, the greater the stable value is, and the shorter the oscillation time of the negativity is. Thus we can adjust the direction and value of the external magnetic field to obtain the maximal entanglement, and avoid the adverse effects of external environment in some initial state. This is feasible within the cun＇ent experimental technology.

Entanglement Evolution of Three-Qubit States under Local Decoherence

By using negativity as entanglement measure,we have investigated the effect of local decoherence from anon-Markovian environment on the time evolution of entanglement of three-qubit states including the GHZ state,the Wstate,and the Werner state.From the results,we find that the entanglement dynamics depends not only on the couplingstrengths but also on the specific states of concern.Specifically,the entanglement takes different behaviors under weakor strong coupling and it varies with the quantum states under study.The entanglement of the GHZ state and theWerner state can be destroyed completely by the local decoherence,while the entanglement of the W state can survivethrough the local decoherence partially.

Influence of Intrinsic Decoherence on Entanglement in Two-Qubit Quantum Heisenberg XYZ Chain

Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.

Entropy Exchange and Entanglement in Superconducting Charge Qubit Inside a Resonant Cavity with Intrinsic Decoherence

By considering the intrinsic decoherence effect, we investigate the entropy exchange and entanglement in the interacting system of a superconducting charge qubit coupled to a single-mode optical cavity. We found that although the intrinsic decoherence leads to an irreversible evolution of the interacting system due to a suppression of coherent quantum features through the decay of off-diagonal matrix elements of the density operator, and has an apparently influence on the partial entropies of the two-component subsystems, it dose not destroy entropy exchange behavior. In addition, the lower bound of the concurrence, as the measure of entanglement of the coupling system, is calculated. It is shown that the evolution of entanglement is sensitive to the change of the intrinsic decoherence.

Effects of intrinsic decoherence on the entanglement of a two-qutrit 1D optical lattice chain with nonlinear coupling

We have investigated the intrinsic decoherence on the entanglement of a two-qutrit one-dimensional （1D） optical lattice chain with nonlinear coupling. As a measure of the entanglement, the negativity of the system is calculated. It is shown that the influence of intrinsic decoherence on the entanglement varies in different initial systems.

Entanglement of two atoms in two-mode Raman coupled model with intrinsic decoherence

Considering intrinsic decoherence, the two-atom two-mode Raman coupled model is investigated in this paper. Utilizing the constants of motion in this model, we obtain the analytic expressions of the density operator of the system for investigating the entanglement of two atoms. The speed of entanglement decay increases with the increasing of the coupling coefficient of one atom. The difference between the oscillation periods when the initial state parameter of atomic subsystem belongs to two intervals becomes smaller with the increasing of the coupling coefficient of one atom. The increasing of the initial photon number of the second field can hasten the vanishing of entanglement of atomic subsystem. The robustness of atomic entanglement against decoherence depends on the interval of the initial state parameter of atomic subsystem.

Effect of Intrinsic Decoherence of Milburn's Model on Entanglement of Two-Qutrit States

We model of intrinsic analyze the time evolution of entanglement of two-qutrit system within the framework of Milburn＇s decoherence. The entanglement evolution relies not only on the parameters of system, but also on the concrete states either pure or mixed. The linear entropy used to measure the extent to which the intrinsic decoherenee affects quantum states is evaluated.

Nonlocal advantage of quantum coherence and entanglement of two spins under intrinsic decoherence

We investigate the nonlocal advantage of quantum coherence(NAQC)and entanglement for two spins coupled via the Heisenberg interaction and under the intrinsic decoherence.Solutions of this decoherence model for the initial spin-1/2 and spin-1 maximally entangled states are obtained,based on which we calculate the NAQC and entanglement.In the weak region of magnetic field,the NAQC behaves as a damped oscillation with the time evolves,while the entanglement decays exponentially(behaves as a damped oscillation)for the spin-1/2(spin-1)case.Moreover,the decay of both the NAQC and entanglement can be suppressed significantly by tuning the magnetic field and anisotropy of the spin interaction to some decoherence-rate-determined optimal values.

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 cosθ｜00〉 ＋ sinθ ｜11〉 and cos Ф ｜01〉 ＋ sin Ф10〉 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 Ф ｜01〉 sinФ｜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.

Intrinsic Decoherence on Two-Qubit Heisenberg XX Chain

Quantum teleportation is investigated by using the entangled states of two-qubit Heisenberg XX chain in an external uniform magnetic field as resources in the model of Milburn＇s intrinsic decoherence. Though intrinsic decoherence on quantum entanglement and quantum teleportation exerts different effects in different initial systems, proper magnetic fields and probabilities of different eigenstates in the initial states can weaken the effects.

Effects of inhomogeneous couplings between atoms and a cavity field on entanglement dynamics

Based on the concept of concurrence, we have investigated the entanglement dynamics of two two-level atoms coupled to a single-mode cavity field with inhomogeneous couplings. We find that, for some initial states, the inho- mogeneous couplings not only induce but also enhance the entanglement in the process of its evolution. In addition, considering the intrinsic decoherence proposed by Milburn, we also find that a proper value of inhomogeneous couplings can enhance the stationary entanglement, and as a result, the destructive effect of intrinsic decoherence on entanglement can be moderated by the inhomogeneous couplings.

Entanglement of Two Atoms Induced by a Fock State of Radiation Field

Considering the intrinsic decoherence proposed by Milburn, we investigate the entanglement between two two-level atoms induced by a Fock state of single-mode quantized radiation field. The time-dependent reduced density matrix of the atoms system is given explicitly, Due to the intrinsic decoheronce, the atoms system will approach a stationary state, where the stationary entanglement depends on the initial states of the field and the atoms.

内禀退相干条件下非线性相互作用对量子纠缠和保真度的影响

通过求解Milburn方程,研究了包含非线性相互作用的Heisenberg自旋链模型中量子纠缠和平均保真度的动力学特性,讨论了非线性相互作用和不同初始态对量子纠缠及平均保真度退相干的影响。结果表明:系统处于铁磁或反铁磁会导致量子纠缠随非线性相互作用的变化不同,相互作用处于铁磁情形比反铁磁时纠缠变化明显;不同初始态对应不同的平均保真度表现,初始态的选择会影响系统的量子通信特性。

在不同初态下Dzyaloshinskii-Moriya相互作用及内禀退相干对海森伯系统的量子纠缠的影响

研究了存在内禀退相干时,对于不同的系统初态,具有DM相互作用和各向异性的三粒子XXZ海森伯模型的对纠缠动力学特性.得出了一些结论:系统的对纠缠度与各向异性参数?无关,但内禀退相干对系统的纠缠有明显的抑制作用;在内禀退相干存在时,若系统初态为纠缠态,选择合适的DM相互作用的参数,系统的对纠缠有一个非零的稳定值;系统初态为分离态时,系统的对纠缠会随时间震荡衰减,并且每次震荡会出现纠缠突然死亡现象,系统的对纠缠最终达到解纠缠状态.因此,选择合适的系统初态和DM相互作用参数可以有效地控制系统的对纠缠.

单模光场与二能级原子的纠缠的内禀退相干(英文)

在一个考虑了内禀退相干的单模光场与二能级原子的耦合系统中,平均光子数,激发态的概率和退相干系数如何影响纠缠随时间演化还并不清楚.Jaynes-Cummings模型被用来描述光场与原子间相互作用.用concurrence下限来计算纠缠度.模拟的结果表明纠缠度随着退相干系数的增加或平均光子数的减少而增加.当激发态的概率在0至0.1之间,纠缠度随着的概率增加而减少;当激发态的概率在0.1至1之间,纠缠度随着的概率增加而增加.无论以上参数取何值,纠缠度都随着时间而减少.

单模热腔场中两原子的纠缠演化动力学

在考虑内禀消相干影响下,通过使用部分转置的负本征值(NPT)和共生纠缠度来度量原子间的纠缠.研究了两个二能级原子与初态为热态的单模光场相互作用系统中,两原子间的纠缠随时间演化问题.讨论了内禀消相干和平均光子数等对纠缠度的影响.结果表明:存在内禀消相干时随着时间的演化,原子间的纠缠逐渐减小到一个确定值.通过对两种不同的纠缠度量方法的比较,可以看出NPT和共生纠缠度的时间演化有相似的规律,能够度量同类系统的纠缠.

两粒子XXZ海森堡系统中的量子纠缠动力学

研究了考虑内禀退相干情况下,两粒子XXZ海森堡系统中量子纠缠在各种外界因素影响下的动态演化规律。研究发现无论系统的初态是否处于最大纠缠态,内禀退相干都会对系统纠缠的含时演化有明显的抑制作用。如果系统的初态为纠缠态|ψ(0)〉=c|01〉+d|10〉,系统的纠缠与各向异性参数和外加磁场没有关系,却受到Dzyaloshinskii-Moriya(DM)相互作用程度和内禀退相干因素的明显影响;如果系统的初态为纠缠态|ψ(0)〉=a|00〉+b|11〉,系统的纠缠与DM相互作用大小和各向异性参数无关,纠缠程度不仅要受到内禀退相干因素的影响,还会被外加磁场进一步削弱。

不同方向Dzyaloshinskii-Moriya相互作用和磁场对自旋系统纠缠和保真度退相干的影响

通过求解系统的Milburn方程,研究了包含Dzyaloshinskii-Moriya相互作用的自旋链系统中纠缠和保真度的动力学演化特性,讨论了不同方向Dzyaloshinskii-Moriya相互作用、不同方向均匀和非均匀磁场、不同初始态对纠缠以及保真度退相干的影响.研究发现,非均匀磁场的引入能够抑制纠缠退相干的发生,初始态的选择对系统纠缠状态的影响很大,可以通过调制Dzyaloshinskii-Moriya相互作用的方向来获得所需纠缠和较高的保真度.研究还发现,退相干条件下,无论是均匀还是非均匀磁场对于保真度的提高并不明显.纠缠和保真度随初始态角度的变化具有周期性,可以根据需要来选取不同系统中的最优初始态.

内禀退相干下海森伯XY模型中的热纠缠性质及其相干调控

通过求解系统的Milburn方程,研究了内禀退相干下两比特海森伯XY模型中的热纠缠性质.讨论了非均匀磁场、系统初始纠缠度、两比特的相对相位对系统热纠缠的调控作用.结果表明:在系统一定的初始条件下,磁场的引入能够大大提高两比特间的热纠缠程度;在固有退相干存在的情况下,系统热纠缠强烈依赖于两个自旋比特的初始态,通过控制两自旋比特的相对相位和振幅,可以获得系统的稳定热纠缠.结果还表明:在没有外界磁场时,发现Bell正交态是系统的"暗态",它的热纠缠度在演化过程中不受系统内禀退相干的影响.