Cosmological quantum entanglement

TL;DR

This paper reviews how quantum entanglement arises in cosmological settings, especially in expanding universes, and discusses its implications for cosmic structure formation, potential observational signatures, and laboratory analogues.

Contribution

It synthesizes recent theoretical and experimental research on cosmological quantum entanglement, highlighting new insights into its role in universe expansion and structure formation.

Findings

Entanglement is produced by spacetime expansion in quantum fields.

Entanglement signatures can distinguish curvature effects from thermal heating.

Quantum fluctuations and entanglement influence the formation of cosmic structures.

Abstract

We review recent literature on the connection between quantum entanglement and cosmology, with an emphasis on the context of expanding universes. We discuss recent theoretical results reporting on the production of entanglement in quantum fields due to the expansion of the underlying spacetime. We explore how these results are affected by the statistics of the field (bosonic or fermionic), the type of expansion (de Sitter or asymptotically stationary), and the coupling to spacetime curvature (conformal or minimal). We then consider the extraction of entanglement from a quantum field by coupling to local detectors and how this procedure can be used to distinguish curvature from heating by their entanglement signature. We review the role played by quantum fluctuations in the early universe in nucleating the formation of galaxies and other cosmic structures through their conversion into classical density anisotropies during and after inflation. We report on current literature attempting to account for this transition in a rigorous way and discuss the importance of entanglement and decoherence in this process. We conclude with some prospects for further theoretical and experimental research in this area. These include extensions of current theoretical efforts, possible future observational pursuits, and experimental analogues that emulate these cosmic effects in a laboratory setting.