Li Hui, Xie Jie, Kwon Hyukjoon, Zhao Yixin, Kim M S, Zhang Lijian
National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation, and Collaborative Innovation Center of Advanced Microstructures, College of Engineering and Applied Sciences and School of Physics, Jiangsu Physical Science Research Center, Nanjing University, Nanjing 210093, China.
School of Computational Sciences, Korea Institute for Advanced Study, Seoul 02455, Korea.
Sci Adv. 2025 May 30;11(22):eadq6014. doi: 10.1126/sciadv.adq6014.
Fluctuation theorems have elevated the second law of thermodynamics to a statistical realm by establishing a connection between time-forward and time-reversal probabilities, providing invaluable insight into nonequilibrium dynamics. While well established in classical systems, their quantum generalization, incorporating coherence and the diversity of quantum noise, remains open. We report the experimental validation of a quantum fluctuation theorem (QFT) in a photonic system, applicable to general quantum processes with nonclassical characteristics, including quasi-probabilistic descriptions of entropy production and multiple time-reversal processes. Our experiment confirms that the ratio between the quasi-probabilities of the time-forward and any multiple time-reversal processes obeys a generalized Crooks QFT. Moreover, coherence induced by a quantum process leads to the imaginary components of quantum entropy production, governing the phase factor in the QFT. These findings underscore the fundamental symmetry between a general quantum process and its time reversal, providing an elementary toolkit to explore noisy quantum information processing.
涨落定理通过建立正向时间和时间反演概率之间的联系，将热力学第二定律提升到了统计领域，为非平衡动力学提供了宝贵的见解。虽然在经典系统中已得到充分确立，但包含相干性和量子噪声多样性的量子推广仍然悬而未决。我们报告了在光子系统中对量子涨落定理（QFT）的实验验证，该定理适用于具有非经典特征的一般量子过程，包括熵产生的准概率描述和多个时间反演过程。我们的实验证实，正向时间和任何多个时间反演过程的准概率之比服从广义的克鲁克斯QFT。此外，量子过程诱导的相干性导致量子熵产生的虚部，它决定了QFT中的相位因子。这些发现强调了一般量子过程与其时间反演之间的基本对称性，为探索有噪声的量子信息处理提供了一个基本工具包。
