Repulsive Gravitational Force as a Witness of the Quantum Nature of Gravity

Abstract:We show that a single spatially superposed 'source' mass acting on a 'probe' matter wavepacket can reveal the quantum nature of the gravitational field. For this we use a specific state preparation and measurement of the superposed source mass, including a postselection, which altogether results in a repulsive gravitational force on the probe particle. A classical gravitational field can never lead to repulsion, as the effect requires quantum interference of two distinct states of gravity. The eventual observation of such an effect would be a violation of Einstein's theory of general relativity, where gravity is always attractive. We also present a calculation in the Heisenberg picture under the formalism of weak values that illustrates how repulsion is achieved. Finally, we estimate the range of parameters (masses and the spatio-temporal extent of interference) for which the experiment is feasible.

5 pages, 2 figures. v2: Discussions were improved. Minor errors were fixed

arXiv:2602.12266 [quant-ph]

(or arXiv:2602.12266v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2602.12266 Focus to learn more arXiv-issued DOI via DataCite

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