Quantum Geometry and Interferometry

TL;DR

This paper explores the idea that quantum geometry at the Planck scale could cause detectable deviations from classical space-time, which can be tested with high-precision interferometry experiments.

Contribution

It proposes that quantum-geometrical degrees of freedom may produce observable macroscopic effects, and describes a laboratory experiment to test these predictions.

Findings

Potential detection of quantum-geometrical fluctuations

Entanglement of positions of separate bodies due to quantum geometry

A high-precision interferometry experiment is underway at Fermilab

Abstract

All existing experimental results are currently interpreted using classical geometry. However, there are theoretical reasons to suspect that at a deeper level, geometry emerges as an approximate macroscopic behavior of a quantum system at the Planck scale. If directions in emergent quantum geometry do not commute, new quantum-geometrical degrees of freedom can produce detectable macroscopic deviations from classicality: spatially coherent, transverse position indeterminacy between any pair of world lines, with a displacement amplitude much larger than the Planck length. Positions of separate bodies are entangled with each other, and undergo quantum-geometrical fluctuations that are not describable as metric fluctuations or gravitational waves. These fluctuations can either be cleanly identified or ruled out using interferometers. A Planck-precision test of the classical coherence of space-time on a laboratory scale is now underway at Fermilab.