Typical Positivity of Nonequilibrium Entropy Production for Pure States

TL;DR

This paper demonstrates that for most pure states, the entropy production during nonequilibrium dynamics is positive and matches ensemble predictions, relying on dynamical typicality and continuity without assuming non-integrability.

Contribution

It shows that entropy production positivity for pure states is typical and does not depend on non-integrability, extending the understanding of second laws in quantum thermodynamics.

Findings

Entropy production matches ensemble predictions for most pure states.

Positivity of entropy production is established under broad nonequilibrium conditions.

Results do not rely on non-integrability assumptions.

Abstract

We establish that the nonequilibrium dynamics of most pure states gives rise to the same entropy production as that of the corresponding ensemble, provided the effective dimension of the ensemble is large enough. This establishes the positivity of entropy production under a wide variety of nonequilibrium situations. Our results follow from dynamical typicality and suitable continuity properties alone, without relying on non-integrability, and they complement other recent efforts to establish "pure state second laws". An explicit comparison with the distinctively different two-point measurement scheme is also provided.