Broadband limits on stochastic length fluctuations from a pair of table-top interferometers

TL;DR

The QUEST experiment uses two highly sensitive table-top interferometers to set new upper limits on broadband stochastic length fluctuations, providing the first constraints at frequencies between 13 and 80 MHz.

Contribution

This work presents the first broadband constraints on stochastic gravitational wave backgrounds using a pair of co-located, quantum-enhanced interferometers at MHz frequencies.

Findings

Set new upper limits on correlated length fluctuations from 13 to 80 MHz.

Achieved a strain sensitivity of 3×10⁻²⁰ 1/√Hz at 40 MHz.

Demonstrated the most sensitive table-top interferometric system to date.

Abstract

The Quantum-Enhanced Space-Time (QUEST) experiment consists of a pair of co-located Power Recycled Michelson Interferometers, each designed to have a broadband, shot-noise limited displacement sensitivity of $2\times10^{-19}$ $\mathrm{m/\sqrt{Hz}}$ from 1 to 200 MHz. Here we present the first results of QUEST that set new upper limits on correlated length fluctuations from 13 to 80 MHz, constituting the first broadband constraints for a stochastic gravitational wave background at these frequencies. In a coincident observing run of $10^{4}$ s the averaging of the cross-correlation spectra between the two interferometer signals resulted in a strain sensitivity of $3\times10^{-20}$ $\mathrm{1/\sqrt{Hz}}$ at 40 MHz, making QUEST the most sensitive table-top interferometric system to date.