Dynamics of fluctuations in a quantum system

TL;DR

This paper investigates the complex dynamics of fluctuations in a far-from-equilibrium quantum system, revealing their sensitivity to quantum properties and potential to inform on correlation dynamics.

Contribution

It provides a detailed comparison of quantum and classical evolution of fluctuations in laser-aligned molecules, highlighting the unique quantum features of uncertainty dynamics.

Findings

Fluctuations exhibit intricate dynamics independent of expectation values.

Quantum properties significantly influence the evolution of uncertainties.

Fluctuation dynamics can reveal information about quantum correlations.

Abstract

"\textit{The noise is the signal}"[R. Landauer, Nature \textbf{392}, 658 (1998)] emphasizes the rich information content encoded in fluctuations. This paper assesses the dynamical role of fluctuations of a quantum system driven far from equilibrium, with laser-aligned molecules as a physical realization. Time evolutions of the expectation value and the uncertainty of a standard observable are computed quantum mechanically and classically. We demonstrate the intricate dynamics of the uncertainty that are strikingly independent of those of the expectation value, and their exceptional sensitivity to quantum properties of the system. In general, detecting the time evolution of the fluctuations of a given observable provides information on the dynamics of correlations in a quantum system.