Thermalization induced by quantum scattering

TL;DR

This paper investigates how quantum scattering with wave-packets leads to decoherence and thermalization of a quantum system, depending on wave-packet width and system degeneracy, with implications for experimental quantum physics.

Contribution

It derives the scattering map for a quantum system interacting with wave-packets and shows how wave-packet width influences decoherence and thermalization processes.

Findings

Narrow wave-packets induce decoherence in non-degenerate systems.

Ensemble of narrow packets causes thermalization of the system.

Broad wave-packets can maintain coherences and prevent thermalization.

Abstract

We use quantum scattering theory to study a fixed quantum system Y subject to collisions with massive particles X described by wave-packets. We derive the scattering map for system Y and show that the induced evolution crucially depends on the width of the incident wave-packets compared to the level spacing in Y . If Y is non-degenerate, sequential collisions with narrow wave-packets cause Y to decohere. Moreover, an ensemble of narrow packets produced by thermal effusion causes Y to thermalize. On the other hand, broad wave-packets can act as a source of coherences for Y , even in the case of an ensemble of incident wave-packets given by the effusion distribution, preventing thermalization. We illustrate our findings on several simple examples and discuss the consequences of our results in realistic experimental situations.