Decoherence of spin superposition state caused by a quantum electromagnetic field

TL;DR

This paper analyzes how a quantum electromagnetic field causes decoherence in a superposed spin-1/2 particle, distinguishing local and nonlocal effects and showing increased decoherence at higher field temperatures.

Contribution

It introduces a detailed categorization of decoherence effects due to quantum electromagnetic fields on spin superpositions, including local and nonlocal factors.

Findings

Decoherence is caused by spin-magnetic field coupling.

Decoherence increases with the temperature of the quantum field.

Two types of decoherence are identified: local and nonlocal.

Abstract

In this study, we investigate the decoherence of a spatially superposed electrically neutral spin-$\frac12$ particle in the presence of a relativistic quantum electromagnetic field in Minkowski spacetime. We demonstrate that decoherence due to the spin-magnetic field coupling can be categorized into two distinct factors: local decoherence, originating from the two-point correlation functions along each branch of the superposed trajectories, and nonlocal decoherence, which arises from the correlation functions between the two superposed trajectories. These effects are linked to phase damping and amplitude damping. We also show that if the quantum field is prepared in a thermal state, decoherence monotonically increases with the field temperature.