We study the physical mechanism of Maxwell's Demon (MD) helping to do extra work in thermodynamic cycles, by describing measurement of position, insertion of wall and information erasing of MD in a quantum mechanical fashion. The heat engine is exemplified with one molecule confined in an infinitely deep square potential inserted with a movable solid wall, while the MD is modeled as a two-level system (TLS) for measuring and controlling the motion of the molecule. It is discovered that the the MD with quantum coherence or on a lower temperature than that of the heat bath of the particle would enhance the ability of the whole work substance formed by the system plus the MD to do work outside. This observation reveals that the role of the MD essentially is to drive the whole work substance being off equilibrium, or equivalently working with an effective temperature difference. The elaborate studies with this model explicitly reveal the effect of finite size off the classical limit or thermodynamic limit, which contradicts the common sense on Szilard heat engine (SHE). The quantum SHE's efficiency is evaluated in detail to prove the validity of second law of thermodynamics.
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 Second Law of Thermodynamics and Quantum Feedback Control: Maxwell's Demon with Weak Measurements
最近Sagawa和Ueda [Phys. Rev. Lett. 100，080403（2008）]导出了可以使用反馈控制从量子系统中提取的功的界限。他们留下了一个问题，即控制器所能进行的每一次测量是否都能达到这个界限。我们表明，它可以，这是直接从最近的工作麦克斯韦的恶魔由Alicki等人[开放系统。戴纳姆11，205（2004）]，用于离散和连续反馈控制。我们的分析还表明，裸露的，有效的测量总是做非负功的系统在平衡状态下，但不增加热量。
Bosonic statistics enhance Maxwell's demon in photonic experiment
MESA+ Institute for Nanotechnology, University of Twente（特温特大学 MESA+ 纳米技术研究所）；Joint Center for Quantum Information and Computer Science, NIST and University of Maryland（美国国家标准与技术研究院与马里兰大学量子信息与计算机科学联合中心）；Department of Physics, University of Maryland（马里兰大学物理系）；Department of Physics and Astronomy, University of Rochester（罗切斯特大学物理与天文学系）；Institute for Physical Science and Technology, University of Maryland（马里兰大学物理科学与技术研究所）
