The reduced state of a small system strongly coupled to a thermal bath may be athermal and used as a small battery once disconnected. The unitarily extractable energy (a.k.a. ergotropy) will be negligible if the disconnecting process is too slow. To study the efficiency of this battery, we consider the cycle of disconnecting, extracting, and connecting the battery back to the bath. Efficiency, i.e. the ratio between ergotropy and connecting plus disconnecting work, is a function of disconnecting time. We consider the Caldeira–Leggett model of a quantum battery in two scenarios. In the first scenario, we assume that the discharged battery is uncorrelated to the bath when connecting back and find that the efficiency peaks at an optimal disconnecting time. In the second scenario, the discharged battery is correlated to the bath, and see that the optimal efficiency corresponds to an instantaneous disconnection. On top of these results, we analyze various thermodynamic quantities for these Caldeira–Leggett quantum batteries and express the first and second laws of thermodynamics for the cycles in simple form despite the system-bath initial correlations and strong coupling regime of the working device.

中文翻译：

---

系统浴相关性和有限时间操作提高了耗散量子电池的效率


与热浴强耦合的小型系统的还原态可能是无热的，并且一旦断开连接就可以用作小型电池。如果断开过程太慢，则单一可提取能量（又名ergotropy）将可以忽略不计。为了研究该电池的效率，我们考虑了断开、取出电池以及将电池连接回浴槽的循环。效率，即各向异性与连接功和断开功之间的比率，是断开时间的函数。我们在两种情况下考虑量子电池的卡尔代拉-莱格特模型。在第一种情况下，我们假设连接回来时放电的电池与浴槽不相关，并发现效率在最佳断开时间达到峰值。在第二种情况下，放电的电池与浴槽相关，并且看到最佳效率对应于瞬时断开。除了这些结果之外，我们分析了这些卡尔代拉-莱格特量子电池的各种热力学量，并以简单的形式表达了循环的热力学第一和第二定律，尽管工作装置具有系统浴初始相关性和强耦合机制。