We report on a single-atom energy-conversion quantum device operating as an engine, or a refrigerator, coupled to a quantum load. The ‘working fluid’ consists of the two optical levels of an ion, while the load is one of its vibrational modes, cooled down to the quantum regime. We explore two important differences with classical engines: (1) the presence of a strong generic coupling interaction between engine and load, which can induce correlations between them and (2) the use of nonthermal baths. We examine the ergotropy of the load, which indicates the maximum amount of energy of the load extractable using solely unitary operations. We show that ergotropy rises with the number of engine cycles despite an increase in the information entropy of the load. The increase of ergotropy of the load points to the possibility of using the phonon distribution of a single atom as a form of quantum battery.

我们报告了一个单原子能量转换量子装置，其作为发动机或制冷机运行，并耦合至量子负载。“工作流体”由离子的两个光学能级组成，而载荷是其振动模式之一，冷却到量子态。我们探讨了经典发动机的两个重要区别：（1）发动机和负载之间存在强大的通用耦合相互作用，这可能会引起它们之间的相关性；（2）使用非恒温浴。我们检查了负载的人体工程学，它表示仅使用单一操作即可提取的负载的最大能量。我们显示，尽管负载的信息熵增加了，但随着发动机循环次数的增加，遍历性也会增加。