Testing the quantum nature of gravity through interferometry
Phys. Rev. D 113, 022002 – Published 6 January, 2026
DOI: https://doi.org/10.1103/15n3-zzjw
Abstract
We propose a Michelson-type interferometric protocol for testing the quantum nature of gravity, in the sense of experimentally probing whether gravity can consistently remain classical when coupled to quantum systems. This is achieved by testing the phenomenology of semiclassical gravity theory in the nonrelativistic limit, which predicts a state-dependent Schrödinger-Newton (SN) evolution of the test mass. The protocol exploits the asymmetry of the SN self-gravity term to generate crosstalk between the common and differential motion of the test masses. This crosstalk can be detected via correlation measurements of the outgoing light field, providing a clean binary signature. Our results show that, when assisted by 10 dB squeezed input states, three hours of aggregated measurement data suffice to achieve an SNR sufficient to conclusively test the SN theory in a 1 Kelvin environment. These findings demonstrate a relatively strong feasibility of using interferometric protocols to experimentally probe whether gravity can remain classical or must exhibit quantum features.
