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arXiv 1601.06402quant-phcond-mat.stat-mech
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量子统计系综关于局域测量的稳定性

Stability of Quantum Statistical Ensembles with Respect to Local Measurements

Walter Hahn, Boris V. Fine

摘要:

我们引入了一个描述宏观系统的量子统计系综的稳定性判据。当少量的局部测量不能显著改变系统总能量的概率分布时,系综被称为“稳定的”。我们将这个标准应用到自旋为1/2的晶格中,从而表明正则系综几乎是稳定的,而具有更广泛能量分布的统计系综是不稳定的。在量子统计物理学基础的背景下,这个结果证明了使用具有窄能量分布的统计系综的合理性,例如正则系综或微正则系综。

英文摘要:

We introduce a stability criterion for quantum statistical ensembles describing macroscopic systems. An ensemble is called "stable" when a small number of local measurements cannot significantly modify the probability distribution of the total energy of the system. We apply this criterion to lattices of spins-1/2, thereby showing that the canonical ensemble is nearly stable, whereas statistical ensembles with much broader energy distributions are not stable. In the context of the foundations of quantum statistical physics, this result justifies the use of statistical ensembles with narrow energy distributions such as canonical or microcanonical ensembles.

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