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arXiv 1802.06758quant-ph
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量子相干性在能量传递热力学中的作用

Role of quantum coherence in the thermodynamics of energy transfer

Ivan Henao, Roberto M. Serra

摘要:

最近的研究热力学箭头的时间,在微观尺度上,质疑其方向的普遍性。理论研究表明,量子关联可以用来恢复自然热流(从热物体到冷物体),这对热力学第二定律提出了明显的挑战。在最近的一个实验(arXiv:1711.03323)中,通过使用两个最初量子关联的自旋系统,观察到了这种“异常”热流。然而,这一有趣的现象与允许它的初始条件之间的确切关系并不完全明显。在这里,我们在更广泛的角度来解决能量转移,确定一个非经典的贡献,适用于逆转的热流以及更一般形式的能量交换。我们推导出三个定理,描述两个微观系统之间的能量转移,任意初始二分态。利用这些定理,我们得到了一个分析界,表明某种类型的量子相干性可以优化这样的过程,优于非相干态。这种真正的量子优势通过两个量子比特之间能量转移的表征得到证实。对于这个系统,它表明,足够大的相干性是必要的,足以恢复热力学箭头的时间。作为所提出的定理的第二个重要结果,我们引入了一类只允许单向能量流的非平衡态。通过这种方式,我们扩大了第二定律的标准克劳修斯陈述适用的集合。

英文摘要:

Recent research on the thermodynamic arrow of time, at the microscopic scale, has questioned the universality of its direction. Theoretical studies showed that quantum correlations can be used to revert the natural heat flow (from the hot body to the cold one), posing an apparent challenge to the second law of thermodynamics. Such an "anomalous" heat current was observed in a recent experiment (arXiv:1711.03323), by employing two spin systems initially quantum correlated. Nevertheless, the precise relationship between this intriguing phenomenon and the initial conditions that allow it is not fully evident. Here, we address energy transfer in a wider perspective, identifying a nonclassical contribution that applies to the reversion of the heat flow as well as to more general forms of energy exchange. We derive three theorems that describe the energy transfer between two microscopic systems, for arbitrary initial bipartite states. Using these theorems, we obtain an analytical bound showing that certain type of quantum coherence can optimize such a process, outperforming incoherent states. This genuine quantum advantage is corroborated through a characterization of the energy transfer between two qubits. For this system, it is shown that a large enough amount of coherence is necessary and sufficient to revert the thermodynamic arrow of time. As a second crucial consequence of the presented theorems, we introduce a class of nonequilibrium states that only allow unidirectional energy flow. In this way, we broaden the set where the standard Clausius statement of the second law applies.

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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