Witnessing the non-classical nature of gravity in the presence of unknown interactions

TL;DR

This paper improves protocols to empirically demonstrate gravitationally induced entanglement, making experiments more feasible and robust against unknown interactions and decoherence, thus advancing tests of quantum gravity.

Contribution

It introduces an improved spin witness protocol that reduces experimental challenges and enhances the robustness of gravitational entanglement detection.

Findings

New witness reduces required interaction time

Statistical analysis separates gravitational effects from other interactions

Proposes closing loopholes with state tomography

Abstract

General relativity as a classical field theory does not predict gravitationally induced entanglement, as such, recent proposals seek an empirical demonstration of this feature which would represent a significant milestone for physics. We introduce improvements to a spin witness protocol that reduce the highly challenging experimental requirements. After rigorously assessing approximations from the original proposal [S. Bose et al. Phys. Rev. Lett. 119, 240401 (2017)], we focus on entanglement witnessing. We propose a new witness which greatly reduces the required interaction time, thereby making the experiment feasible for higher decoherence rates, and we show how statistical analysis can separate the gravitational contribution from other possibly dominant and ill-known interactions. We point out a potential loophole and show how it can be closed using state tomography.