Experimental limits for low-frequency space-time fluctuations from ultrastable optical resonators

TL;DR

This study uses cryogenic sapphire optical interferometers to set experimental upper limits on low-frequency space-time fluctuations, constraining quantum gravity models and the random-walk hypothesis.

Contribution

It provides the first experimental limits on very low-frequency space-time fluctuations using ultrastable cryogenic optical resonators.

Findings

Upper limit of 1.10^-24 Hz^-1 at 6 microHz

Upper limit of 1.10^-28 Hz^-1 above 5 mHz

Constraints on the random-walk hypothesis parameter

Abstract

It has been suggested that space-time might undergo fluctuations because of its intrinsic quantum nature. These fluctuations would pose a fundamental limit to the ability of measuring distances with arbitrary precision, beyond any limitations due to standard quantum mechanics. Laser interferometers have recently been proposed as being suited for a search for the existence of space-time fluctuations. Here we present results of a search for space-time fluctuations of very low fluctuation frequencies, in the range from 1 microHz to 0.5 Hz. Rigid optical interferometers made out of sapphire and operated at cryogenic temperature were used. We find an upper limit of 1.10^-24 Hz^-1 for the normalized distance noise spectral density at 6 microHz, and of 1.10^-28 Hz^-1 above 5 mHz, and establish an experimental limit for the parameter of a recently proposed random-walk hypothesis.