How cosmological expansion affects communication between distant quantum systems

TL;DR

This paper investigates how the expansion of the universe influences quantum communication between distant systems, revealing that cosmological effects can enhance classical communication capacity and encode information about cosmic dynamics.

Contribution

It introduces a quantum communication protocol in an expanding universe and demonstrates how cosmological parameters affect its capacity and potential to reveal cosmic information.

Findings

Cosmological expansion increases the classical capacity of quantum communication.

The capacity is sensitive to the universe's equation of state parameter w.

The protocol can encode information about the universe's coupling with quantum fields.

Abstract

A quantum communication protocol between harmonic oscillator detectors, interacting with a quantum field, is developed in a cosmological expanding background. The aim is to see if the quantum effects arising in an expanding universe, such as the cosmological particle production, could facilitate the communication between two distant parts or if they provide an additive noisy effect. By considering a perfect cosmic fluid, the resulting expansion turns out to increase the classical capacity of the protocol. This increasing occurs for all the cosmological expansions unless the latter is sharpened just before the receiver's detector interacts with the field. Moreover, the classical capacity turns out to be sensible to the barotropic parameter $w$ of the perfect fluid and to the coupling between the field and the scalar curvature $\xi$. As a consequence, by performing this protocol, one can achieve information about the cosmological dynamics and its coupling with a background quantum field.