Experimental prospects for detecting the quantum nature of spacetime

Abstract

This thesis is concerned with advancing the confrontation between relativistic quantum information (RQI) and experiment. We investigate the lessons that some present-day experiments can teach us about the relationship between quantum information, relativistic motion and gravitation.

First, we look at the insights we can gain within the framework of quantum field theory in curved spacetimes. Particularly, we propose a generalization of the superconducting circuit simulation of the dynamical Casimir effect where we consider relativistically moving boundary conditions following different trajectories. We study the feasibility of extending the experimental setup to reproduce richer relativistic trajectories.

Next, motivated by recent efforts to describe the gravitational interaction as a classical channel arising from continuous quantum measurements, we study what types of dynamics can emerge from a collisional model of repeated interactions between a system and a set of ancillae. We use these results in the context of gravitational interactions and show how our general framework recovers the gravitational decoherence model of Kafri, Taylor and Milburn (KTM).

Finally, we argue that single-atom interference experiments achieving large spatial superpositions can rule out a particular realization of the KTM model where gravitational interactions act pairwise between massive particles as classical channels, approximating Newtonian pair-potential at low energies. Our findings counteract the present belief that gravity-inspired decoherence models cannot be confronted by experiment. Specifically, we find experimental indications which show that if gravity does reduce to pairwise Newtonian interactions between atoms in a non-relativistic limit, these interactions cannot be fundamentally classical.

Our work shows that state-of-the-art technology can be used as a tool to test the quantum character of spacetime and that further efforts should be spent in analyzing how current experimental setups can guide us towards building a complete theory of quantum gravity.