Decoherence and Recoherence in Model Quantum Systems

TL;DR

This paper explores quantum decoherence mechanisms and demonstrates how coupling electrons to a squeezed vacuum state can lead to recoherence, with implications for quantum interference experiments.

Contribution

It introduces the concept of recoherence via squeezed vacuum states and analyzes its potential observability in electron interferometry.

Findings

Decoherence can be suppressed below vacuum level using squeezed states.

Recoherence is related to violations of the weak energy condition.

Estimates suggest possible experimental observation of recoherence effects.

Abstract

We discuss the various manifestations of quantum decoherence in the forms of dephasing, entanglement with the environment, and revelation of "which-path" information. As a specific example, we consider an electron interference experiment. The coupling of the coherent electrons to the quantized electromagnetic field illustrates all of these versions of decoherence. This decoherence has two equivalent interpretations, in terms of photon emission or in terms of Aharonov-Bohm phase fluctuations. We consider the case when the coherent electrons are coupled to photons in a squeezed vacuum state. The time-averaged result is increased decoherence. However, if only electrons which are emitted during selected periods are counted, the decoherence can be suppressed below the level for the photon vacuum. This is the phenomenon of recoherence. This effect is closely related to the quantum violations of the weak energy condition, and is restricted by similar inequalities. We give some estimates of the magnitude of the recoherence effect and discuss prospects for observing it in an electron interferometry experiment.