Binary gravitational waves as probes of quantum graviton states

TL;DR

This paper proposes that gravitational waves from binary systems could reveal nonclassical graviton states, such as squeezed states from inflation, by exhibiting sub-Poissonian statistics similar to quantum light.

Contribution

It introduces the idea that graviton vacuum states may be nonclassical, enabling gravitational wave observations to probe quantum properties of gravitons from the early Universe.

Findings

Gravitational waves can carry signatures of nonclassical graviton states.

Squeezed graviton states from inflation may be detectable via binary system observations.

Gravitational wave statistics could reveal quantum features of gravity.

Abstract

It is well known that the most reliable way to reveal the quantum nature of light is through photon number statistics, since photons exhibiting sub-Poissonian statistics unambiguously demonstrate their quantum behavior. In this paper, we show that gravitons emitted by binary systems can, in principle, exhibit analogous sub-Poissonian statistics. The key idea is that the vacuum state of gravitons may not be the standard Minkowski vacuum but rather a nonclassical state imprinted with the physics of the early Universe, such as inflation. Accordingly, gravitational waves from binary systems provide a means to probe the graviton states generated in the early Universe. As a concrete example, we show that squeezed graviton states originating from inflation may be detected through the observation of gravitational waves from binary systems.