Energy Transport in Closed Quantum Systems

TL;DR

This paper investigates energy transport in closed quantum systems with discrete spectra, revealing how quantum advection modes influence energy flow and differ from classical continuous-spectrum models.

Contribution

It introduces the concept of quantum advection modes as Landauer channels in discrete spectra and analyzes their correlation with energy flux in perturbed quantum systems.

Findings

Some modes positively correlate with energy flow.

Other modes anticorrelate, causing backflow of probability.

Energy transport differs from classical continuous-spectrum systems.

Abstract

We examine energy transport in an ensemble of closed quantum systems driven by stochastic perturbations. One can show that the probability and energy fluxes can be described in terms of quantum advection modes (QAM) associated with the off-diagonal elements of the density matrix. These QAM play the role of Landauer channels in a system with discrete energy spectrum and the eigenfunctions that cannot be described as plane waves. In order to determine the type of correlations that exist between the direction and magnitudes of each QAM and the average direction of energy and probability fluxes we have numerically solved the time-dependent Schr\"{o}dinger equation describing a single particle trapped in a parabolic potential well which is perturbed by stochastic 'ripples'. The ripples serve as a localized energy source and are offset to one side of the potential well. As the result a non-zero net energy flux flows from one part of the potential well to another across the symmetry center of the potential. We find that some modes exhibit positive correlation with the direction of the energy flow. Other modes, that carry a smaller energy per unit of the probability flux, anticorrelate with the energy flow and thus provide a backflow of the probability. The overall picture of energy transport that emerges from our results is very different from the conventional one based on a system with continuous energy spectrum.