We introduce a class of quantum heat engines which consists of two-energy-eigenstate systems, the simplest of quantum mechanical systems, undergoing quantum adiabatic processes and energy exchanges with heat baths, respectively, at different stages of a cycle. Armed with this class of heat engines and some interpretation of heat transferred and work performed at the quantum level, we are able to clarify some important aspects of the second law of thermodynamics. In particular, it is not sufficient to have the heat source hotter than the sink, but there must be a minimum temperature difference between the hotter source and the cooler sink before any work can be extracted through the engines. The size of this minimum temperature difference is dictated by that of the energy gaps of the quantum engines involved. Our new quantum heat engines also offer a practical way, as an alternative to Szilard's engine, to physically realise Maxwell's daemon. Inspired and motivated by the Rabi oscillations, we further introduce some modifications to the quantum heat engines with single-mode cavities in order to, while respecting the second law, extract more work from the heat baths than is otherwise possible in thermal equilibria. Some of the results above are also generalisable to quantum heat engines of an infinite number of energy levels including 1-D simple harmonic oscillators and 1-D infinite square wells.
Overcoming the Quasi-Static Bottleneck: A Finite-Time Quantum Otto Information Engine Achieving Near-Unity Efficiency
College of Physics, Jilin University（吉林大学物理学院）；Department of Chemistry and Department of Physics and Astronomy, State University of New York at Stony Brook（纽约州立大学石溪分校化学系和物理与天文学系）
Unbounded Work Extraction and Zero Work Fluctuations in a Super-Carnot Otto Information Engine
College of Physics, Jilin University（吉林大学物理学院）；Department of Chemistry and Department of Physics and Astronomy, State University of New York at Stony Brook（纽约州立大学石溪分校化学系和物理与天文学系）
Quantum process inference for a single qubit Maxwell's demon
虽然量子测量理论是围绕密度矩阵和可观测量建立的，但热力学热力学定律是基于热机和制冷机中使用的过程。量子热力学的研究融合了这两种不同的范式。在这篇文章中，我们强调使用量子过程矩阵作为一种统一的语言来描述量子制度中的热力学过程。我们的实验表明，这在量子麦克斯韦恶魔的背景下，其中两个主要的量通常进行调查;平均工作提取$\langle W \rangle$和功效$γ$，它的措施如何有效地反馈操作使用所获得的信息。利用量子过程矩阵的工具，我们开发了这两个量的最佳反馈协议，并在超导电路QED装置中进行了实验研究。
The Filtering Demon: Beyond Standard Thermodynamic Bounds and Harnessing Measurement Error and Quantum Friction
College of Physics, Jilin University（吉林大学物理学院）；Department of Chemistry and Department of Physics and Astronomy, State University of New York at Stony Brook（纽约州立大学石溪分校化学系和物理与天文学系）
Amplifying microwave pulses with a single qubit engine fueled by quantum measurements
Ecole Normale Supérieure de Lyon（里昂高等师范学院）；CNRS, Laboratoire de Physique（法国国家科学研究中心物理实验室）；Inria, LIP（法国国家数字技术研究研究所计算物理实验室）；Université de Lorraine（洛林大学）；MajuLab, CNRS-UCA-SU-NUS-NTU International Joint Research Laboratory（马久实验室（中法新联合研究实验室））；Centre for Quantum Technologies, National University of Singapore（新加坡国立大学量子技术中心）
Finite-Time Optimization of Quantum Szilard heat engine
Graduate School of China Academy of Engineering Physics（中国工程物理研究院研究生学院）；Department of Physics, Peking University（北京大学物理学院）；Department of Physics, Beijing Normal University（北京师范大学物理学院）；Beijing Computational Science Research Center（北京计算科学研究中心）
Geometry-Induced Vacuum Polarization and Mode Shifts in Maxwell-Klein-Gordon Theory
Joint Center for Particle, Nuclear Physics and Cosmology（粒子、核物理与宇宙学联合中心）；Department of Physics, Nanjing University（南京大学物理系）；School of Physics and Electrical Engineering, Linyi University（临沂大学物理与电气工程学院）
