2020/08/31 by Giulia Rubino, Gonzalo Manzano, Časlav Brukner
Mathematics · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Arrow #Arrow of time #Classical mechanics #Computer science #Entropy (arrow of time) #Entropy production #Irreversible process #Mathematics #Physics #Quantum #Quantum Mechanics and Applications #Quantum mechanics #Second law of thermodynamics #Statistical Mechanics and Entropy #Statistical physics #Superposition principle #Time evolution #Uncertainty principle #quant-ph
paper · pdf · doi:10.1038/s42005-021-00759-1
published as Commun. Phys. 4, 251 (2021) · 15 pages, 6 figures. Accepted version
arxiv created 2021/11/26 · openalex publication_date 2021/11/26 · arxiv updated 2021/11/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract Microscopic physical laws are time-symmetric, hence, a priori there exists no preferential temporal direction. However, the second law of thermodynamics allows one to associate the “forward” temporal direction to a positive variation of the total entropy produced in a thermodynamic process, and a negative variation with its “time-reversal” counterpart. This definition of a temporal axis is normally considered to apply in both classical and quantum contexts. Yet, quantum physics admits also superpositions between forward and time-reversal processes, whereby the thermodynamic arrow of time becomes quantum-mechanically undefined. In this work, we demonstrate that a definite thermodynamic time’s arrow can be restored by a quantum measurement of entropy production, which effectively projects such superpositions onto the forward (time-reversal) time-direction when large positive (negative) values are measured. Finally, for small values (of the order of plus or minus one), the amplitudes of forward and time-reversal processes can interfere, giving rise to entropy-production distributions featuring a more or less reversible process than either of the two components individually, or any classical mixture thereof.