Abstract
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.
- Received 23 May 2022
- Revised 7 September 2022
- Accepted 8 September 2022
DOI:https://doi.org/10.1103/PhysRevLett.129.170604
© 2022 American Physical Society
Physics Subject Headings (PhySH)
synopsis
Microscopic Reversibility Goes Quantum
Published 20 October 2022
A fundamental principle in statistical mechanics called microscopic reversibility has been extended to the quantum world.
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