On inference of quantization from gravitationally induced entanglement

TL;DR

This paper critically examines proposals to detect quantum gravity via gravitationally induced entanglement, highlighting interpretational ambiguities and the limited conclusiveness of such tests, while emphasizing their potential to explore new quantum regimes.

Contribution

It demonstrates that entanglement tests cannot definitively determine the mediating nature of gravity and discusses how cosmological observations already provide some insights into quantum aspects of gravity.

Findings

Entanglement generation can be described by mediators or non-local processes.

Relativity does not enforce a local channel for entanglement.

Cosmological data already show some quantum features of gravity.

Abstract

Observable signatures of the quantum nature of gravity at low energies have recently emerged as a promising new research field. One prominent avenue is to test for gravitationally induced entanglement between two mesoscopic masses prepared in spatial superposition. Here we analyze such proposals and what one can infer from them about the quantum nature of gravity, as well as the electromagnetic analogues of such tests. We show that it is not possible to draw conclusions about mediators: even within relativistic physics, entanglement generation can equally be described in terms of mediators or in terms of non-local processes -- relativity does not dictate a local channel. Such indirect tests therefore have limited ability to probe the nature of the process establishing the entanglement as their interpretation is inherently ambiguous. We also show that cosmological observations already demonstrate some aspects of quantization that these proposals aim to test. Nevertheless, the proposed experiments would probe how gravity is sourced by spatial superpositions of matter, an untested new regime of quantum physics.