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arXiv 1301.0233cond-mat.stat-mechquant-ph
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淬灭自旋链中的量子赫兹熵增加

Quantum Hertz entropy increase in a quenched spin chain

Darshan G. Joshi, Michele Campisi

摘要:

经典的赫兹熵是由恒定能量表面限定的相空间体积的对数;它的量子对应物,量子赫兹熵,是$\hat S = k_B \ln \hat N$,其中量子算符$\hat N$指定能量低于给定能量本征态的状态的数量。最近已经证明,当一个孤立的量子力学系统被一个外部驱动器驱动出平衡时,其量子赫兹熵的期望值的变化不可能是负的,并且对于绝热驱动是零。这完全符合克劳修斯原理。在这里,我们测试的情况下,当两个相同的XY自旋链最初在不同的温度淬火成一个单一的XY链的量子赫兹熵的期望的行为。我们没有观察到量子赫兹熵减少。这一发现进一步支持了量子赫兹熵是孤立量子系统的真熵的说法。我们进一步量化了淬灭链离热平衡有多远以及最接近平衡的温度。

英文摘要:

The classical Hertz entropy is the logarithm of the volume of phase space bounded by the constant energy surface; its quantum counterpart, the quantum Hertz entropy, is $\hat S = k_B \ln \hat N$, where the quantum operator $\hat N$ specifies the number of states with energy below a given energy eigenstate. It has been recently proved that, when an isolated quantum mechanical system is driven out of equilibrium by an external driving, the change in the expectation of its quantum Hertz entropy cannot be negative, and is null for adiabatic driving. This is in full agreement with the Clausius principle. Here we test the behavior of the expectation of the quantum Hertz entropy in the case when two identical XY spin chains initially at different temperatures are quenched into a single XY chain. We observed no quantum Hertz entropy decrease. This finding further supports the statement that the quantum Hertz entropy is a proper entropy for isolated quantum systems. We further quantify how far the quenched chain is from thermal equilibrium and the temperature of the closest equilibrium.

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