Testing Quantum Gravity

TL;DR

This paper proposes a practical experimental approach using macroscopic quantum systems to test whether gravity exhibits quantum properties, potentially enabling empirical validation of quantum gravity theories.

Contribution

It introduces a feasible method to detect quantum gravity effects with current technology, bridging the gap between theory and experiment in quantum gravity research.

Findings

Quantum gravity effects could be observable with existing technology.

Failure to observe quantum gravity effects would imply gravity is purely classical.

The approach could falsify or support key aspects of quantum gravity theories.

Abstract

The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a pragmatic way to test if gravitation really occurs between quantum objects or not. In this article we suggest such a potential way out of this deadlock, utilizing macroscopic quantum systems; superfluid helium, gaseous Bose-Einstein condensates and "macroscopic" molecules. It turns out that true quantum gravity effects - here defined as observable gravitational interactions between truly quantum objects - could and should be seen (if they occur in nature) using existing technology. A falsification of the low-energy limit, in the accessible weak-field regime, would also falsify the full theory of quantum gravity, making it enter the realm of testable, potentially falsifiable theories, i.e. becoming real physics after almost a century of pure theorizing. If weak-field gravity between quantum objects is shown to be absent (in the regime where the approximation should apply), we know that gravity then is a strictly classical phenomenon absent at the quantum level.