Can classical theories of gravity produce entanglement?

Abstract

A recent paper published in Nature [Nature,646,813(2025)] claims that quantum particles become entangled through their gravitational interaction, even when the gravitational potential is classical. Here we show that the entanglement found by the authors is a consequence of letting particles diffuse from one object to the other. When this is not allowed, the wavefunction remains factorized. In fact, noticing that entanglement is relative to a chosen partition of the Hilbert space, we show that the choice of partition implicitly made by the authors is such that entanglement arises as soon as particles diffuse, even when no interaction potential is present. Therefore, it is the free evolution, not the classical gravitational potential, which acts as the entangling mechanism in the scenario considered by the authors.

Presentation modified; analysis of an analogous one dimensional lattice added