paper

Irreversibility and the arrow of time in a quenched quantum system

arXiv:1502.06704 · doi:10.1103/PhysRevLett.115.190601

Abstract

Irreversibility is one of the most intriguing concepts in physics. While microscopic physical laws are perfectly reversible, macroscopic average behavior has a preferred direction of time. According to the second law of thermodynamics, this arrow of time is associated with a positive mean entropy production. Using a nuclear magnetic resonance setup, we measure the nonequilibrium entropy produced in an isolated spin-1/2 system following fast quenches of an external magnetic field and experimentally demonstrate that it is equal to the entropic distance, expressed by the Kullback-Leibler divergence, between a microscopic process and its time-reverse. Our result addresses the concept of irreversibility from a microscopic quantum standpoint.

8 pages, 7 figures, RevTeX4-1; Accepted for publication Phys. Rev. Lett

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