Quantum Effect Unique to Gravity Based on the Weak Equivalence Principle in Atomic Interferometry

ABSTRACT

The construction of a quantum gravity theory remains challenging. One of the difficulties is the lack of sufficient experimental evidence. As a first step toward the quantum gravity experiment, Bose et al. proposed a low-energy experiment to test whether or not Newtonian gravity can generate quantum entanglement or not. However, they assumed that only gravity mediates in the system, and their proposals fail when other quantum interactions come into play. A relativistic extension of the BMV proposals would be the key to exploring the quantum nature unique to gravity. In this talk, we investigate an alternative experimental setup that can distinguish gravity-induced entanglement from entanglement resulting from other interactions. Specifically, we consider an interference experiment of an atomic clock particle experiencing a weak gravitational field induced by a superposed mass source. As a result, we find that the atomic interference exhibits non-periodic behavior only when gravity induces entanglement, while it exhibits periodic decoherence and recoherence for the semiclassical treatment of gravity. Furthermore, we discuss that the non-periodic behavior of the visibility does not appear when we consider the Coulomb interaction instead of gravity, and this feature unique to gravity is deeply related to the weak equivalence principle.

This talk is based on the collaborated work with Y. Nambu, S. Maeda and Y. Osawa, published in Phys.Rev.D 106 (2022) 12, 126005.

BIOGRAPHY

Youka Kaku is a Ph.D. student in the QG Laboratory at the Department of Physics at Nagoya University, where she is also a recipient of the JSPS Research Fellowship for Young Scientists. She completed her undergraduate studies at Nagoya University from 2016 to 2020 and earned her master's degree there in 2022. Her research focuses on exploring the intersection of gravity and quantum information, specifically through tabletop experiments designed to test gravity-induced entanglement and the quantum features of non-dynamical curved spacetime.