Quantum signatures in nonlinear gravitational waves

TL;DR

This paper explores quantum signatures in gravitational waves, proposing that quantum optics tools can detect non-classical features like squeezing and sub-Poissonian statistics, potentially revealing quantum gravity effects.

Contribution

It introduces a framework to identify quantum signatures in gravitational waves using quantum optics techniques, enabling detection of quantum gravity effects beyond classical predictions.

Findings

Squeezed-coherent gravitational waves can exhibit sub-Poissonian graviton statistics.

Quantum states of gravitational waves can be reconstructed from optical measurements.

Quantum features of gravity may be detectable with current or near-future interferometers.

Abstract

The effective quantum field theory description of gravity, despite its non-renormalizability, allows for predictions beyond classical general relativity. As we enter the age of gravitational wave astronomy, an important and timely question is whether measurable quantum predictions that depart from classical gravity, analogous to quantum optics effects which cannot be explained by classical electrodynamics, can be found. In this work, we investigate quantum signatures in gravitational waves using tools from quantum optics. Squeezed-coherent gravitational waves, which can exhibit sub-Poissonian graviton statistics, can enhance or suppress the signal measured by an interferometer, a characteristic effect of quantum squeezing. Moreover, we show that Gaussian gravitational wave quantum states can be reconstructed from measurements over an ensemble of optical fields interacting with a single copy of the gravitational wave, thus opening the possibility of detecting quantum features of gravity beyond classical general relativity.