Decoherence in Quantum Mechanics

TL;DR

This paper compares traditional and novel methods for studying decoherence in quantum mechanics, highlighting their effectiveness and limitations in predicting decoherence time scales and entropy generation.

Contribution

It introduces a new correlator approach to decoherence that complements the conventional master equation method, addressing instabilities in entropy calculations.

Findings

Both methods accurately predict decoherence time scales.

The perturbative master equation has instabilities affecting entropy calculations.

The correlator approach effectively captures entropy generation without instabilities.

Abstract

We study decoherence in a simple quantum mechanical model using two approaches. Firstly, we follow the conventional approach to decoherence where one is interested in solving the reduced density matrix from the perturbative master equation. Secondly, we consider our novel correlator approach to decoherence where entropy is generated by neglecting observationally inaccessible correlators. We show that both methods can accurately predict decoherence time scales. However, the perturbative master equation generically suffers from instabilities which prevents us to reliably calculate the system's total entropy increase. We also discuss the relevance of the results in our quantum mechanical model for interacting field theories.