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arXiv 1302.5231quant-ph
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平衡态附近的纠缠衰落

Fading entanglement near equilibrium state

Gregory B. Furman, Victor M. Meerovich, Vladimir L. Sokolovsky

摘要:

最近的研究表明,处于非平衡态的量子系统中的纠缠可以在比处于平衡态的量子系统中高得多的温度下出现。然而,任何系统都受制于建立平衡的自然松弛过程。对偶极耦合自旋1/2系统从非平衡态到平衡态的纠缠动力学进行了数值研究。自旋系统的特征是一个双温度密度矩阵,平衡的建立过程是在这些温度的均衡。用非平衡统计算符的方法描述系统的演化。首先考虑了在低温下同自旋系统建立平衡态的过程。结果表明,自旋子系统的逆温度的时间依赖性是由一个非线性方程的解决方案,在著名的高温近似的线性方程。首次研究了平衡态建立过程中的纠缠动力学,发现在平衡状态建立过程中,纠缠度随时间和温度的变化呈现非单调的变化。纠缠在系统中建立平衡之前很久就消失了。结果表明,纠缠动力学强烈依赖于塞曼能量与偶极能量的比值。在高比值时,系统中的纠缠度在100 μs左右的时间内迅速下降,而在低比值时,系统平衡的建立和纠缠度的衰落需要长达1 ms的时间。

英文摘要:

It was recently shown that entanglement in quantum systems being in a non-equilibrium state can appear at much higher temperatures than in an equilibrium state. However, any system is subject to the natural relaxation process establishing equilibrium. The work deals with the numerical study of entanglement dynamics in a dipolar coupled spin-1/2 system under the transition from a non-equilibrium state to an equilibrium state. The spin system is characterized by a two-temperature density matrix, and the process of the establishment of equilibrium is in the equalization of these temperatures. The method of the non-equilibrium statistical operator is used to describe the evolution of the system. The process of establishing an equilibrium state in the homonuclear spin systems at low temperature was first considered. It was shown that the time dependences of the inverse temperatures of the spin subsystems are given by a solution of non-linear equations in contrast to the linear equations in the well-known high temperature approximation. It was first studied the entanglement dynamics during the equilibrium state establishment and found that, during establishing equilibrium, the concurrence changes non-monotonically with time and temperatures. Entanglement fades long before equilibrium is established in the system. It was shown that the entanglement dynamics depends strongly on the ratio of the Zeeman energy to the dipolar energy. At a high ratio, the concurrence in the system decreases quickly for time about 100 μs while, at a low ratio, establishment of equilibrium and fading entanglement take prolonged time up to 1 ms.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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