Comments on graviton detection

TL;DR

This paper argues that detecting gravitons or quantum noise in gravitational waves does not prove the quantization of gravity, as classical waves can produce identical signals in detectors, challenging recent claims in the literature.

Contribution

It clarifies that observing signals attributed to gravitons or quantum noise does not constitute evidence for quantum gravity, extending classical optics arguments to gravitational wave detection.

Findings

Detection of gravitons does not imply quantum gravity.

Classical gravitational waves can mimic quantum signals in detectors.

The paper extends classical optics arguments to gravitational wave physics.

Abstract

It is possible to make a detector which clicks after absorbing a single graviton. Similarly, it is possible to make a gravitational wave detector which can see the quantum noise induced by certain highly squeezed states of the graviton. However, contrary to some recent arguments in the literature, observation of either or both of these signals would not constitute proof or even evidence that the gravitational field is quantized. This is a simple technical statement: a classical gravitational wave can produce the same output data in a detector. Here we explain this result, presented earlier in arXiv:2308.12988, which is a straightforward extension of an ancient argument in quantum optics.