Low pumping energy mode of the "optical bars''/"optical lever" topologies of gravitational-wave antennae

TL;DR

This paper discusses a low-energy pumping mode in optical topologies for gravitational-wave detectors, enabling sensitivity surpassing the Standard Quantum Limit with reduced optical energy by leveraging cross-correlation techniques.

Contribution

It introduces a method to further lower the optical pumping energy in optical bar and lever topologies using cross-correlation of noise, approaching the internal loss limit.

Findings

Sensitivity about ten times better than SQL achievable

Optical pumping energy can be reduced by an order of magnitude

Method applicable to current and planned gravitational-wave detectors

Abstract

The ``optical bars''/``optical lever'' topologies of gravitational-wave antennae allow to obtain sensitivity better that the Standard Quantum Limit while keeping the optical pumping energy in the antenna relatively low. Element of the crucial importance in these schemes is the local meter which monitors the local test mirror position. Using cross-correlation of this meter back-action noise and its measurement noise it is possible to further decrease the optical pumping energy. In this case the pumping energy minimal value will be limited by the internal losses in the antenna only. Estimates show that for values of parameters available for contemporary and planned gravitational-wave antennae, sensitivity about one order of magnitude better than the Standard Quantum Limit can be obtained using the pumping energy about one order of magnitude smaller energy than is required in the traditional topology in order to obtain the the Standard Quantum Limit level of sensitivity.