Distinguishable consequence of classical gravity on quantum matter

TL;DR

This paper proposes a testable way to distinguish classical gravity from quantum gravity by analyzing the phase response in gravitational interactions of coherent masses, highlighting observable differences.

Contribution

It introduces a quantum-classical dynamics framework in Newtonian gravity to identify unique experimental signatures of classical gravity.

Findings

Classical gravity cannot produce quantum entanglement between matter.

Distinct phase responses differentiate classical from quantum gravity.

Experiments with coherent masses can test the classical gravity hypothesis.

Abstract

What if gravity is classical? If true, a consistent co-existence of classical gravity and quantum matter requires that gravity exhibit irreducible fluctuations. These fluctuations can mediate classical correlations, but not quantum entanglement, between the quantized motion of the gravitationally interacting matter. We use a consistent theory of quantum-classical dynamics in the Newtonian limit of gravity to show that experimentally relevant observables can conclusively test the hypothesis that gravity is classical. This can be done for example by letting highly coherent source masses interact with each other gravitationally, and performing precise measurements of the cross-correlation of their motion. Theory predicts a characteristic phase response that distinguishes classical gravity from quantum gravity, and from naive sources of decoherence. Such experiments are imminently viable.