Bellini Marco, Kwon Hyukjoon, Biagi Nicola, Francesconi Saverio, Zavatta Alessandro, Kim M S
Istituto Nazionale di Ottica (CNR-INO), Largo Enrico Fermi 6, 50125 Florence, Italy.
LENS and Department of Physics and Astronomy, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy.
Phys Rev Lett. 2022 Oct 21;129(17):170604. doi: 10.1103/PhysRevLett.129.170604.
The principle of microscopic reversibility lies at the core of fluctuation theorems, which have extended our understanding of the second law of thermodynamics to the statistical level. In the quantum regime, however, this elementary principle should be amended as the system energy cannot be sharply determined at a given quantum phase space point. In this Letter, we propose and experimentally test a quantum generalization of the microscopic reversibility when a quantum system interacts with a heat bath through energy-preserving unitary dynamics. Quantum effects can be identified by noting that the backward process is less likely to happen in the existence of quantum coherence between the system's energy eigenstates. The experimental demonstration has been realized by mixing coherent and thermal states in a beam splitter, followed by heterodyne detection in an optical setup. We verify that the quantum modification for the principle of microscopic reversibility is critical in the low-temperature limit, while the quantum-to-classical transition is observed as the temperature of the thermal field gets higher.
微观可逆性原理是涨落定理的核心，涨落定理已将我们对热力学第二定律的理解扩展到统计层面。然而，在量子领域，这一基本原理应予以修正，因为在给定的量子相空间点上，系统能量无法被精确确定。在本信函中，当一个量子系统通过能量守恒幺正动力学与热库相互作用时，我们提出并通过实验测试了微观可逆性的量子推广。通过注意到在系统能量本征态之间存在量子相干的情况下，反向过程发生的可能性较小，可以识别出量子效应。实验演示是通过在分束器中混合相干态和热态，然后在光学装置中进行外差检测来实现的。我们验证了微观可逆性原理的量子修正在低温极限下至关重要，而随着热场温度升高会观察到量子到经典的转变。
