On Quantum Gravity Tests with Composite Particles

TL;DR

This paper investigates how quantum gravity modifications to fundamental physics can be tested using macroscopic composite particles, addressing the suppression of effects with more constituents and proposing experiments to improve bounds.

Contribution

It provides a detailed analysis of the scaling of quantum gravity corrections in composite particles and offers experimental bounds surpassing previous quantum oscillator tests.

Findings

Quantum gravity corrections are suppressed with more constituents, but this can be bounded experimentally.

Tight bounds on quantum gravity effects are achieved using macroscopic pendula.

Proposed experiments could further strengthen bounds and improve test sensitivity.

Abstract

Models of quantum gravity imply a fundamental revision of our description of position and momentum that manifests in modifications of the canonical commutation relations. Experimental tests of such modifications remain an outstanding challenge. These corrections scale with the mass of test particles, which motivates experiments using macroscopic composite particles. Here we consider a challenge to such tests, namely that quantum gravity corrections of canonical commutation relations are expected to be suppressed with increasing number of constituent particles. Since the precise scaling of this suppression is unknown, it needs to be bounded experimentally and explicitly incorporated into rigorous analyses of quantum gravity tests. We analyse this scaling based on concrete experiments involving macroscopic pendula and provide tight bounds that exceed those of current experiments based on quantum mechanical oscillators. Furthermore, we discuss possible experiments that promise even stronger bounds thus bringing rigorous and well-controlled tests of quantum gravity closer to reality.