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arXiv 1012.4762quant-phcond-mat.stat-mech
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用静态路径加随机相位近似描述热纠缠

Description of thermal entanglement with the static path plus random-phase approximation

N. Canosa, J. M. Matera, R. Rossignoli

摘要:

本文讨论了静态路径加随机相位近似(SPA+RPA)和随后的平均场+RPA处理方法在有限温度下计算复合量子系统纠缠度中的应用。这些方法只涉及局部对角化和广义集体振动频率的确定。作为例证,我们评估了在有限温度下,在横向磁场$b$中,$n$自旋的完全连接XXZ链中的成对纠缠。结果表明,平均场+RPA已经提供了一个准确的分析描述的并发下面的平均场临界区($|b|<b_c$),大$n$的精确,而完整的SPA+RPA是能够改善有限系统的临界区域的结果。同时还证明了当基态是可分的($|b|>b_c$)时,$T>0$的弱纠缠也会出现,而对于$|b|<b_c$和$|b|>b_c$,两两纠缠的极限温度表现出截然不同的区域.

英文摘要:

We discuss the application of the static path plus random phase approximation (SPA+RPA) and the ensuing mean field+RPA treatment to the evaluation of entanglement in composite quantum systems at finite temperature. These methods involve just local diagonalizations and the determination of the generalized collective vibrational frequencies. As illustration, we evaluate the pairwise entanglement in a fully connected XXZ chain of $n$ spins at finite temperature in a transverse magnetic field $b$. It is shown that already the mean field+RPA provides an accurate analytic description of the concurrence below the mean field critical region ($|b|<b_c$), exact for large $n$, whereas the full SPA+RPA is able to improve results for finite systems in the critical region. It is proved as well that for $T>0$ weak entanglement also arises when the ground state is separable ($|b|>b_c$), with the limit temperature for pairwise entanglement exhibiting quite distinct regimes for $|b|<b_c$ and $|b|>b_c$.

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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