Quantum Gravity in a Laboratory?

TL;DR

This paper examines the potential of tabletop gravitationally induced entanglement experiments to serve as evidence of quantum gravity, analyzing their feasibility, interpretation, and significance within current scientific paradigms.

Contribution

It critically assesses the claims of GIE experiments as witnesses of quantum gravity and discusses the philosophical and practical implications of their potential success.

Findings

GIE experiments could provide evidence of quantum gravity under certain models

The interpretation of GIE results as witnesses of quantum gravity is ambiguous

Performing GIE experiments would be a significant scientific achievement regardless of their interpretative outcome

Abstract

It has long been thought that observing distinctive traces of quantum gravity in a laboratory setting is effectively impossible, since gravity is so much weaker than all the other familiar forces in particle physics. But the quantum gravity phenomenology community today seeks to do the (effectively) impossible, using a challenging novel class of `tabletop' Gravitationally Induced Entanglement (GIE) experiments, surveyed here. The hypothesized outcomes of the GIE experiments are claimed by some (but disputed by others) to provide a `witness' of the underlying quantum nature of gravity in the non-relativistic limit, using superpositions of Planck-mass bodies. We inspect what sort of achievement it would possibly be to perform GIE experiments, as proposed, ultimately arguing that the positive claim of witness is equivocal. Despite various sweeping arguments to the contrary in the vicinity of quantum information theory or given low-energy quantum gravity, whether or not one can claim to witness the quantum nature of the gravitational field in these experiments decisively depends on which out of two legitimate modelling paradigms one finds oneself in. However, by situating GIE experiments in a tradition of existing experiments aimed at making gravity interestingly quantum in the laboratory, we argue that, independently of witnessing or paradigms, there are powerful reasons to perform the experiments, and that their successful undertaking would indeed be a major advance in physics.