Decoherence and Dynamical Entropy Generation in Quantum Field Theory

TL;DR

This paper introduces a new method to quantify decoherence in quantum field theory by neglecting inaccessible correlators, demonstrating entropy increase from pure states to thermal states, and comparing with existing approaches.

Contribution

It presents a novel decoherence formalism in quantum field theory and relates entropy growth to physical decay rates, addressing limitations of previous methods.

Findings

Entropy of pure states increases to thermal entropy in the model

Decoherence rate matches the single particle decay rate

Perturbative master equations exhibit secular growth issues

Abstract

We formulate a novel approach to decoherence based on neglecting observationally inaccessible correlators. We apply our formalism to a renormalised interacting quantum field theoretical model. Using out-of-equilibrium field theory techniques we show that the Gaussian von Neumann entropy for a pure quantum state increases to the interacting thermal entropy. This quantifies decoherence and thus measures how classical our pure state has become. The decoherence rate is equal to the single particle decay rate in our model. We also compare our approach to existing approaches to decoherence in a simple quantum mechanical model. We show that the entropy following from the perturbative master equation suffers from physically unacceptable secular growth.