Quantum Limits of Interferometer Topologies for Gravitational Radiation Detection

TL;DR

This paper systematically compares various interferometer topologies for gravitational wave detection, optimizing their sensitivities and complexities, and finds that frequency-dependent squeezed-light injection with a short filter cavity offers a promising balance of performance and robustness.

Contribution

It provides a comprehensive comparison and optimization of interferometer topologies, offering practical guidelines for future gravitational-wave detector enhancements.

Findings

Frequency-dependent squeezed-light injection improves broadband sensitivity.

A hundred-meter filter cavity balances sensitivity and complexity.

Robustness against optical loss is achievable with optimized configurations.

Abstract

In order to expand the astrophysical reach of gravitational wave detectors, several interferometer topologies have been proposed to evade the thermodynamic and quantum mechanical limits in future detectors. In this work, we make a systematic comparison among them by considering their sensitivities and complexities. We numerically optimize their sensitivities by introducing a cost function that tries to maximize the broadband improvement over the sensitivity of current detectors. We find that frequency-dependent squeezed-light injection with a hundred-meter scale filter cavity yields a good broadband sensitivity, with low complexity, and good robustness against optical loss. This study gives us a guideline for the near-term experimental research programs in enhancing the performance of future gravitational-wave detectors.