Entanglement Structure in Expanding Universes

TL;DR

This paper studies how quantum entanglement behaves in expanding universes, specifically in de Sitter spacetime, revealing that entanglement becomes undetectable beyond the Hubble horizon, which supports the classical nature of inflationary fluctuations.

Contribution

It demonstrates how entanglement detection between detectors in de Sitter space is limited by the Hubble horizon, linking quantum properties to classical cosmological phenomena.

Findings

Entanglement cannot be detected beyond the Hubble horizon.

Supports the classicalization of quantum fluctuations during inflation.

Uses a particle detector model to analyze entanglement in curved spacetime.

Abstract

We investigate entanglement of a quantum field in de Sitter spacetime using a particle detector model. By considering the entanglement between two comoving detectors interacting with a scalar field, it is possible to detect the entanglement of the scalar field by swapping it to detectors. For the massless minimal scalar field, we find that the entanglement between the detectors cannot be detected when their physical separation exceeds the Hubble horizon scale. This behavior supports the appearance of the classical nature of quantum fluctuations generated during the inflationary era.