Gravitational entanglement witness through Einstein ring image

Building a theory of quantum gravity remains a significant challenge, primarily due to the lack of experimental evidence.

As a first step toward quantum gravity experiments, Bose et al. proposed a low-energy experiment to test whether Newtonian gravity can generate quantum entanglement. Recent work has extended this proposal to relativistic region, investigating quantum entanglement induced by curved spacetime beyond the Newtonian framework.
In this talk, we examine the interplay between quantum theory and gravity by exploring gravitational lensing and Einstein ring images in a weak gravitational field induced by a mass source in spatial quantum superposition. We focus on the behavior of a quantum massless scalar field propagating in this background spacetime. Additionally, we propose an observable, the which-path information indicator, that reveals the presence of Einstein rings and serves as evidence for gravity-induced entanglement. This study lays the groundwork for further exploration of quantum effects in general relativistic phenomena.

The talk is based on collaborative work with Yasusada Nambu (arXiv:2411.12997).