Gravity entanglement, quantum reference systems, degrees of freedom

Gravity mediated entanglement (GME) has been proposed as the first experimentally testable signature of quantum gravity. However, to what extent the effect is due to quantum gravity is under debate. In this note, we argue in several ways that the observation of GME does indeed tell us something new about gravity compared to previous experiments. In particular, we consider a quantum reference frame treatment of the experiment that allows us to pinpoint the single degree of freedom responsible for the effect. We also discuss the relevance of the Newtonian limit, the longitudinal/transverse decomposition of the field, and the local operations and classical communication theorem. Our conclusion is that experiments trying to detect GME would be interesting because (a) either positive or negative results would be able to falsify several theories (b) observation of GME would represent something truly novel.