Liu Junjie, Jung Kenneth A, Segal Dvira
Department of Chemistry and Centre for Quantum Information and Quantum Control, University of Toronto, 80 Saint George St., Toronto, Ontario M5S 3H6, Canada.
Department of Chemistry, Stanford University, Stanford, California 94305, USA.
Phys Rev Lett. 2021 Nov 12;127(20):200602. doi: 10.1103/PhysRevLett.127.200602.
Theoretical treatments of periodically driven quantum thermal machines (PD-QTMs) are largely focused on the limit-cycle stage of operation characterized by a periodic state of the system. Yet, this regime is not immediately accessible for experimental verification. Here, we present a general thermodynamic framework that handles the performance of PD-QTMs both before and during the limit-cycle stage of operation. It is achieved by observing that periodicity may break down at the ensemble average level, even in the limit-cycle phase. With this observation, and using conventional thermodynamic expressions for work and heat, we find that a complete description of the first law of thermodynamics for PD-QTMs requires a new contribution, which vanishes only in the limit-cycle phase under rather weak system-bath couplings. Significantly, this contribution is substantial at strong couplings even at limit cycle, thus largely affecting the behavior of the thermodynamic efficiency. We demonstrate our framework by simulating a quantum Otto engine building upon a driven resonant level model. Our results provide new insights towards a complete description of PD-QTMs, from turn-on to the limit-cycle stage and, particularly, shed light on the development of quantum thermodynamics at strong coupling.
对周期性驱动量子热机（PD-QTMs）的理论处理主要集中在以系统的周期性状态为特征的极限环运行阶段。然而，这一 regime 并非能立即通过实验验证。在此，我们提出一个通用的热力学框架，该框架可处理PD-QTMs在极限环运行阶段之前及期间的性能。这是通过观察到即使在极限环阶段，周期性也可能在系综平均水平上被打破而实现的。基于这一观察，并使用功和热的传统热力学表达式，我们发现对PD-QTMs的热力学第一定律的完整描述需要一个新的贡献，该贡献仅在相当弱的系统-热库耦合下的极限环阶段才会消失。值得注意的是，即使在极限环时，这种贡献在强耦合下也很大，从而在很大程度上影响热力学效率的行为。我们通过基于驱动共振能级模型模拟量子奥托发动机来展示我们的框架。我们的结果为从开启到极限环阶段对PD-QTMs的完整描述提供了新的见解，特别是为强耦合下量子热力学的发展提供了启示。
