Quantum recoherence in the early universe

¹ Université Paris-Saclay, CNRS, Institut d'Astrophysique Spatiale - 91405, Orsay, France
² Laboratoire Astroparticule et Cosmologie, Université Denis Diderot Paris 7 - 10 rue Alice Domon et Léonie Duquet, 75013 Paris, France
³ Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, CNRS, Université PSL, Sorbonne Université, Université Paris Cité - F-75005 Paris, France

^(a) E-mail: thomas.colas@universite-paris-saclay.fr (corresponding author)

Received: 6 April 2023
Accepted: 12 June 2023

Abstract

Despite being created through a fundamentally quantum-mechanical process, cosmological structures have not yet revealed any sign of genuine quantum correlations. Among the obstructions to the direct detection of quantum signatures in cosmology, environmental-induced decoherence is arguably one of the most inevitable. Yet, we discover a mechanism of quantum recoherence for the adiabatic perturbations when they couple to an entropic sector. After a transient phase of decoherence, a turning point is reached, recoherence proceeds and adiabatic perturbations exhibit a large amount of self-coherence at late-time. This result is also understood by means of a non-Markovian master equation, which reduces to Wilsonian effective-field theory in the unitary limit. This allows us to critically assess the validity of open-quantum-system methods in cosmology and to highlight that re(de)coherence from linear interactions has no flat-space analogue.