The Holometer: An Instrument to Probe Planckian Quantum Geometry

TL;DR

The Holometer is a novel instrument designed to detect quantum correlations in space-time at the Planck scale, surpassing current gravitational wave detectors in sensitivity.

Contribution

It introduces a new experimental setup with two co-located interferometers to probe quantum geometry at Planckian scales, enabling tests beyond existing gravitational wave observatories.

Findings

Achieved shot-noise-limited sensitivity in measurements.

Constrained models of quantum geometry at the Planck scale.

Projected to test a broad class of quantum gravity theories.

Abstract

This paper describes the Fermilab Holometer, an instrument for measuring correlations of position variations over a four-dimensional volume of space-time. The apparatus consists of two co-located, but independent and isolated, 40m power-recycled Michelson interferometers, whose outputs are cross-correlated to 25 MHz. The data are sensitive to correlations of differential position across the apparatus over a broad band of frequencies up to and exceeding the inverse light crossing time, 7.6 MHz. A noise model constrained by diagnostic and environmental data distinguishes among physical origins of measured correlations, and is used to verify shot-noise-limited performance. These features allow searches for exotic quantum correlations that depart from classical trajectories at spacelike separations, with a strain noise power spectral density sensitivity smaller than the Planck time. The Holometer in current and future configurations is projected to provide precision tests of a wide class of models of quantum geometry at the Planck scale, beyond those already constrained by currently operating gravitational wave observatories.