Entanglement production in the decay of a metastable state

TL;DR

This paper investigates the entanglement generated during the decay of a metastable state into radiation, analyzing how entanglement evolves between the system and radiation over time using Gaussian models.

Contribution

It introduces a method to quantify entanglement between radiation fragments at different times using windowed Fourier transforms in Gaussian models.

Findings

Entanglement entropy increments serve as effective measures of entanglement.

The study clarifies the relationship between system-radiation and late-early radiation entanglement.

Results are relevant for understanding entanglement in Hawking radiation.

Abstract

When a metastable state decays into radiation, there must be entanglement between the radiation and the decaying system, as well as between radiation collected at late and early times. We study the interplay between these two types of entanglement in simple Gaussian models in the Markov approximation. We define, via a windowed Fourier transform, multimode quantum states associated with radiation fragments produced at different times and compute the corresponding entanglement entropy increments. On the basis of these results, we argue that such entropy increments are useful entanglement measures, especially in cases, such as Hawking radiation, where one wishes to separate the radiation into ``old'' and ``new.''