Signatures of the Quantization of Gravity at Gravitational Wave Detectors

TL;DR

This paper develops a formalism to analyze how quantum states of gravity affect gravitational wave detectors, suggesting that detecting quantum-induced noise could reveal the quantization of gravity and gravitons.

Contribution

It introduces a new formalism to compute detector responses to various quantum states of gravitational fields, highlighting potential observable effects of gravity quantization.

Findings

Quantum noise varies with the gravitational field's quantum state.

Coherent states produce minimal effects, while non-coherent states can significantly enhance noise.

Detection of such noise could provide evidence for gravitons.

Abstract

We develop a formalism to calculate the response of a model gravitational wave detector to a quantized gravitational field. Coupling a detector to a quantum field induces stochastic fluctuations ("noise") in the length of the detector arm. The statistical properties of this noise depend on the choice of quantum state of the gravitational field. We characterize the noise for vacuum, coherent, thermal, and squeezed states. For coherent states, corresponding to classical gravitational configurations, we find that the effect of gravitational field quantization is small. However, the standard deviation in the arm length can be enhanced -- possibly significantly -- when the gravitational field is in a non-coherent state. The detection of this fundamental noise could provide direct evidence for the quantization of gravity and for the existence of gravitons.