Optimisation of table-top 3D interferometers for Observational Quantum Gravity

TL;DR

This paper discusses the design and optimization of 3D interferometers for quantum gravity experiments, focusing on increasing sensitivity through higher circulating power and mode cleaning techniques.

Contribution

It introduces a novel interferometer design with enhanced sensitivity and a new output mode cleaner to suppress higher-order modes, enabling better detection of quantum space-time fluctuations.

Findings

Achieved displacement sensitivity surpassing previous experiments.

Designed an output mode cleaner to reduce contrast defect modes.

Outlined strategies for increasing circulating power without detector saturation.

Abstract

With the use of twin, co-located, 3D interferometers, Cardiff University's Gravity Exploration Institute aims to observe quantum fluctuations of space-time as predicted by some theories of quantum gravity. Our design displacement sensitivity exceeds that of previous similar experiments, which have constrained the magnitudes of the fluctuations in the 1-25 MHz band. The increased sensitivity comes in large part from the comparably higher circulating power we aim to achieve, which reduces the overall shot noise. One complication of higher circulating power is an increase in contrast defect light, which includes higher-order modes. We will use the DC-readout scheme, whose dark-fringe offset must sufficiently dominate the contrast defect in order to detect faint signals. However, too much total output power risks saturating the high-bandwidth photodetectors. Suppressing the higher-order mode content of the contrast defect is a key strategy to realising the high circulating power and eliminating non-signal-carrying power that contributes to shot noise. For this, the inclusion of an output mode cleaner, whose design is described, is required.