Universal signature of quantum entanglement across cosmological distances. (15th December 2022)

• Record Type: Journal Article
• Authors: Brahma, Suddhasattwa; Berera, Arjun; Calderón-Figueroa, Jaime
• Is Part Of: Classical and quantum gravity. Volume 39:Number 24(2022)
• Publication Date: 2022-12-15
• Subjects: inflation -- entanglement -- open quantum system -- primordial vacuum fluctuations -- scalar perturbations; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/1361-6382/aca066
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: Although the paradigm of inflation has been extensively studied to demonstrate how macroscopic inhomogeneities in our Universe originate from quantum fluctuations, most of the established literature ignores the crucial role that entanglement between the modes of the fluctuating field plays in its observable predictions. In this paper, we import techniques from quantum information theory to reveal hitherto undiscovered predictions for inflation which, in turn, signals how quantum entanglement across cosmological scales can affect large scale structure. Our key insight is that observable long-wavelength modes must be part of an open quantum system, so that the quantum fluctuations can decohere in the presence of an environment of short-wavelength modes. By assuming the simplest model of single-field inflation, and considering the leading order interaction term from the gravitational action, we derive a universal lower bound on the observable effect of such inescapable entanglement. Although this signal is too weak for direct detection in the foreseeable future, we discuss the importance of its theoretical implications.