An instability of unitary quantum dynamics

TL;DR

This paper explores the theoretical possibility of a spontaneous breakdown of unitarity in quantum dynamics, revealing an instability that could have profound implications for understanding quantum evolution and its fundamental principles.

Contribution

It introduces the concept of a potential instability in quantum dynamics where unitarity can spontaneously break down due to extreme sensitivity to perturbations.

Findings

Existence of a theoretical instability in quantum dynamics.

Implications for environmental sensitivity and fundamental unitarity.

Discussion of potential violations of quantum principles.

Abstract

Instabilities of equilibrium quantum mechanics are common and well-understood. They are manifested for example in phase transitions, where a quantum system becomes so sensitive to perturbations that a symmetry can be spontaneously broken. Here, we consider the possibility that the time evolution governing quantum dynamics may be similarly subject to an instability, at which its unitarity spontaneously breaks down owing to an extreme sensitivity towards perturbations. We find that indeed such an instability exists, and we explore its immediate consequences. Interpretations of the results both in terms of extreme sensitivity to the influence of environmental degrees of freedom, and in terms of a possible fundamental violation of unitarity are discussed.