Bose-Marletto-Vedral experiment without observable spacetime superpositions

TL;DR

This paper demonstrates that gravity can generate entanglement without spacetime superpositions by using non-locally tomographic models, challenging the necessity of quantum spacetime degrees of freedom in quantum gravity tests.

Contribution

It introduces toy models showing entanglement generation via non-locally tomographic gravitational mediators without requiring spacetime superpositions.

Findings

Entanglement can be generated without spacetime superpositions.

Non-locally tomographic couplings enable gravitational entanglement.

Models include fermionic, anyonic, and bit anti-bit systems.

Abstract

Reconciling quantum mechanics and general relativity remains one of the most profound challenges in modern physics. The BMV (Bose-Marletto-Vedral) experiment can assess the quantum nature of gravity by testing whether gravitational interactions can generate entanglement between quantum systems. In this work, we show that entanglement can be generated by gravity without requiring spacetime superpositions or quantum spacetime degrees of freedom by using mediators that do not satisfy the usual property of local tomography when coupling to quantum matter. Specifically, we showcase how entanglement can be generated using three distinct toy models that display non-locally tomographic couplings between quantum matter and a locally classical gravitational mediator. These models include (i) fermionic systems with the parity superselection rule, (ii) non-Abelian anyonic systems, and (iii) a novel bit anti-bit model. Our results demonstrate a crucial point: a gravitational mediator which does not exhibit superpositions of its classical basis but still qualifies as non-classical via non-locally tomographic coupling mechanisms can generate entanglement through local interactions. This work also underscores the importance of relaxing local tomography in exploring the quantum-gravitational interface. It provides a novel perspective on the role of spacetime degrees of freedom in entanglement generation through local interactions.