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  • Open Access

Quantum state of interacting primordial inhomogeneities: Desqueezing and decoherence

Amaury Micheli1,*, Yuto Oshima2, and Tomo Takahashi3

  • *Contact author: amaury.micheli@riken.jp
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Phys. Rev. D 113, 123554 – Published 29 June, 2026

DOI: https://doi.org/10.1103/q7m4-13jf

Abstract

We investigate how interactions affect the quantum state of scalar perturbations during inflation and the quantum correlations they may exhibit. Focusing on the case of scalar perturbations in single-field inflation, we model interactions using a Lindblad equation with a nonunitary contribution quadratic in the scalar perturbations and of parametrizable amplitude and time dependence. We compute the quantum state of these interacting perturbations, which is fully described by its purity and squeezing parameters. First, we show that, on top of the well-studied decrease of purity, interactions asymptotically decrease the squeezing parameter by up to 75%. Second, we show that this desqueezing induced by the interactions, in addition to the purity loss, causes a further suppression of quantum correlations. We thus emphasize that the quantum or classical character of the correlations exhibited by the perturbations cannot be correctly determined by computing the effect of interactions on the purity alone. Since the phenomenological framework adopted in this paper encompasses a wide class of possible interactions, our results provide general insights into the nature of decoherence processes in primordial fluctuations.

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Phys. Rev. D 113, 123554– Published 29 June, 2026
  • Received 8 January 2026
  • Accepted 30 April 2026
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