Quantum decoherence in the entanglement entropy of a composite particle and its relationship to coarse graining in the Husimi function

TL;DR

This paper explores how quantum decoherence in a composite particle's one-body density matrix relates to entanglement entropy growth and coarse graining in phase space, linking quantum and semi-classical descriptions via the Husimi function.

Contribution

It establishes a connection between quantum decoherence, entanglement entropy, and phase space coarse graining in the context of composite particles.

Findings

Quantum decoherence occurs due to two-body correlations in the composite particle.

Entanglement entropy increases with delocalization of the particle.

Semi-classical approximation becomes valid as entanglement entropy grows.

Abstract

I investigate quantum decoherence in a one-body density matrix of a composite particle consisting of two correlated particles. Because of a two-body correlation in the composite particle, quantum decoherence occurs in the one-body density matrix that has been reduced from the two-body density matrix. As the delocalization of the distribution of the composite particle grows, the entanglement entropy increases, and the system can be well-described by a semi-classical approximation, wherein the center position of the composite particle can be regarded as a classical coordinate. I connect the quantum decoherence in the one-body density matrix of a composite particle to the coarse graining in a phase space distribution function of a single particle and associate it with the Husimi function.