Decoherence and entropy production due to quantum fluctuations of spacetime

TL;DR

This paper investigates how quantum fluctuations of spacetime, modeled as gravitons, cause decoherence and entropy production in open quantum systems, revealing fundamental irreversibility in quantum-gravitational interactions.

Contribution

It introduces a detailed analysis of graviton-induced decoherence and entropy production, highlighting universal effects of quantum spacetime fluctuations on quantum systems.

Findings

Gravitons induce decoherence of spatial superpositions over long times

External driving through a graviton bath leads to entropy production

Quantum spacetime fluctuations cause fundamental irreversibility

Abstract

The intersection between quantum mechanics and gravitational physics has been providing challenging puzzles for decades. In this thesis, we study the dynamics of an open quantum system coupled with a bath of gravitons, the quanta of the gravitational field in the linear limit of general relativity. We focus on two main aspects. First, we analyze the decoherence induced by gravitons when we consider the open system to be described by both external and internal degrees of freedom. Since gravity is universal, the internal variables also interact with the gravitons, and here we show that this interaction leads to the decoherence of spatial superpositions of microscopic systems in the long-time regime, even when the graviton bath alone does not. We then proceed to the second main aspect, which is the entropy production that arises when an external agent drives a quantum system through the graviton bath. This irreversibility comes from quantum fluctuations of spacetime itself and, as such, has a fundamentally universal aspect.