Quantum discord in de Sitter space

TL;DR

This paper investigates quantum discord between two modes of a scalar field in de Sitter space, revealing that discord persists even when entanglement vanishes due to increasing curvature, highlighting quantum correlations beyond entanglement.

Contribution

It introduces a novel analysis of quantum discord in de Sitter space, comparing different observer perspectives and showing discord's resilience beyond entanglement loss.

Findings

Entanglement decreases with increasing curvature.

Entanglement vanishes at infinite curvature for certain fields.

Quantum discord remains non-zero even when entanglement disappears.

Abstract

We study quantum discord between two free modes of a massive scalar field in a maximally entangled state in de Sitter space. We introduce two observers, one in a global chart and the other in an open chart of de Sitter space, and the observers determine the quantum discord created by each detecting one of the modes. This situation is analogous to the relationship between an observer in a Minkowski chart and another in one of the two Rindler charts in flat space. We find that the state becomes less entangled as the curvature of the open chart gets larger. In particular, for the cases of a massless, and a conformally coupled scalar field, the entanglement vanishes in the limit of infinite curvature. However, we find that the quantum discord never disappears even in the limit that entanglement disappears.