Collisional decoherence of a tracer particle moving in one dimension

TL;DR

This paper investigates how a tracer particle's quantum coherence is lost in a one-dimensional gas, highlighting phase averaging as the main decoherence mechanism and showing momentum superpositions are more robust than position superpositions.

Contribution

It demonstrates that phase averaging dominates decoherence over information exchange and identifies conditions under which momentum superpositions remain coherent.

Findings

Phase averaging is the primary decoherence mechanism.

Position superpositions decohere quickly, momentum superpositions are more robust.

Superpositions of different momenta resist decoherence until spatial separation occurs.

Abstract

We study decoherence of the external degree of freedom of a tracer particle moving in a one dimensional dilute Boltzmann gas. We find that phase averaging is the dominant decoherence effect, rather than information exchange between tracer and gas particles. While a coherent superposition of two wave packets with different mean positions quickly turns into a mixed state, it is demonstrated that such superpositions of different momenta are robust to phase averaging, until the two wave packets acquire a different position due to the different velocity of each wave packet.