You might also be interested in Bose et al. (2017), "Spin Entanglement Witness for Quantum Gravity" https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11... aka [hep-th] https://arxiv.org/abs/1707.06050 which proposes a way to "certify gravity as a quantum coherent mediator, through simple spin correlation measurements".