基于二比特自旋压缩模型中的热纠缠研究

利用Concurrence判据,讨论了基态和有限温度下二比特自旋压缩模型中的量子热纠缠性质.探究了自旋压缩参量μ、外磁场Ω以及温度T对系统纠缠性质的影响.结果发现,首先,Concurrence随着耦合参量μ(或Ω)的增大先增大到最大值,然后逐渐衰减到零,Concurrence的最大值随参数μ(或Ω)的增大而增大;Concurrence的衰减率会随参数μ(或Ω)的增大而减小,从而可以在较大的范围内得到体系热纠缠.其次,较大的耦合参量取值可以提升Concurrence存在的温度范围.最后,在有限温度条件下,当参数μ(或Ω)取值较小时,体系的纠缠保持为零,即存在纠缠"死亡间隔"现象;然而随着参量μ(或Ω)的取值增大到一定值时,Concurrence会突然产生,即存在纠缠瞬间产生("Sudden birth")现象,值得注意的是:纠缠的"死亡间隔"会随着参数μ(或Ω)的增大而减小.     

Quantum correlations in a two-qubit anisotropic Heisenberg XYZ chain with uniform magnetic field

Quantum correlations in an anisotropic Heisenberg XY Z chain is investigated by use of concurrence C and measurement-induced disturbance(MID). We show that the behaviors of the MID are remarkably different from the concurrence. Firstly, it is shown that there is a revival phenomenon in the concurrence but not in the MID, which is suitable for both the ground state case and the finite temperature case. Based on the analysis of the ground-state C and MID structures,we illustrate the reason why the ground-state MID does not show a revival phenomenon in detail. Then we explore different effects of the external and self parameters on entanglement and MID behaviors. It can be shown that the region of MID is evidently larger than the case of concurrence, and that the concurrence signals a quantum phase transition even at finite T while MID does not. Cases where the concurrence finally maintains one nonzero constant value regardless of the value of the variable B for a constant Jz, while MID decreases monotonously to zero with increasing B. We also show that if B can take a proper range of values, the concurrence decreases with the improvement of the anisotropic parameter γ, whereas an opposite effect for MID behaviors is presented.     

Multi-impurity effects on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field

The effects of multi-impurity on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field are studied. The impurities make the equal pairwise entanglement in a ring compete with each other so that the pairwise entanglement exhibits oscillation. If the impurities are of larger couplings, both the critical temperature and pairwise entanglement can be improved.     

Multi-impurity effects on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field

The effects of multi-impurity on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field are studied. The impurities make the equal pairwise entanglement in a ring compete with each other so that the pairwise entanglement exhibits oscillation. If the impurities are of larger couplings, both the critical temperature and pairwise entanglement can be improved.     

Entanglement Properties Between Two Spatially Separated Atoms with Cascade Configuration in Free Space

We investigate the entanglement properties between two identical atoms with cascade configuration through the retarded dipole-dipole interaction in free space when their spatial separation is on the order of radiation wavelength or less. We analyze the function of Hamiltonian induced by dipole-dipole interaction. By solving master equation, we show that the spontaneous emission induce entanglement and destroy entanglement too. We also show the long life time of entanglement within cascade configuration.     

耗散环境下二比特体系的量子关联性质研究

利用Quantum Discord(QD)判据,研究了与热库相互作用的二比特体系的量子关联性质.讨论了在不同初态下体系量子关联随时间的变化,以及热库的平均光子数m,n和原子的自发辐射率γ对体系量子关联性质的影响.结果表明,在不同的初态下,体系可以得到不同性质的量子关联;而且当原子自发辐射率γ取固定值时,QD的衰减会随m,n取值的减小而减慢,热库平均光子数都为零的情况下能够得到最大范围的量子关联;此外,当热库平均光子数m,n取确定值时,随着γ取值的减小,QD的衰减也会随之减慢,此时同样会得到较大范围的量子关联.说明较小的热库平均光子数以及原子自发辐射率γ能够减弱QD的衰减,从而获得生命力较强的体系量子关联.