Thermality versus objectivity: can they peacefully coexist?

TL;DR

This paper investigates whether quantum systems can simultaneously exhibit thermalization and objectivity, finding that generally they cannot, but under specific conditions such as high temperature or large environments, coexistence is possible.

Contribution

The study analyzes the conditions under which thermal and objective quantum states can coexist, revealing regimes where both properties are compatible.

Findings

Thermal and objective states generally do not coexist.

Coexistence is possible at high temperatures and with large environments.

Everyday objects can be both thermal and objective under certain conditions.

Abstract

Under the influence of external environments, quantum systems can undergo various different processes, including decoherence and equilibration. We observe that macroscopic objects are both objective and thermal, thus leading to the expectation that both objectivity and thermalisation can peacefully coexist on the quantum regime too. Crucially, however, objectivity relies on distributed classical information that could conflict with thermalisation. Here, we examine the overlap between thermal and objective states. We find that in general, one cannot exist when the other is present. However, there are certain regimes where thermality and objectivity are more likely to coexist: in the high temperature limit, at the non-degenerate low temperature limit, and when the environment is large. This is consistent with our experiences that everyday-sized objects can be both thermal and objective.