Classical (and Quantum) Heuristics for Gravitational Wave Detection

TL;DR

This paper derives sensitivity bounds for gravitational wave detectors, comparing classical and quantum schemes, and discusses the challenges of high-frequency gravitational wave detection and the detectability of primordial backgrounds.

Contribution

It provides a unified framework to evaluate the sensitivity of various gravitational wave detectors, focusing on classical schemes and their fundamental limits.

Findings

Sensitivity bounds derived for classical and quantum detectors

High-frequency detection is limited by stored electromagnetic energy and transfer function

Primordial gravitational wave backgrounds are likely undetectable with current interferometers

Abstract

We derive a lower bound on the sensitivity of generic mechanical and electromagnetic gravitational wave detectors. We consider both classical and quantum detection schemes, although we focus on the former. Our results allow for a simple reproduction of the sensitivities of a variety of experiments, including optical interferometers, resonant bars, optomechanical sensors, and electromagnetic conversion experiments. In the high-frequency regime, all detection schemes we consider can be characterised by their stored electromagnetic energy and the signal transfer function, which we provide. We discuss why high-frequency gravitational wave searches are especially difficult and primordial gravitational wave backgrounds might not be detectable above the sensitivity window of existing interferometers.