### Speaker

### Description

If relativistic gravitation has a quantum description, it must be meaningful to consider a spacetime metric in a genuine quantum superposition. Here I present a new operational framework for studying “superpositions of spacetimes” via model particle detectors. After presenting the general approach, I show how it can be applied to describe a spacetime generated by a BTZ black hole in a superposition of masses and how such detectors would respond. The detector exhibits signatures of quantum-gravitational effects reminiscent of Bekenstein’s seminal conjecture concerning the quantized mass spectrum of black holes in quantum gravity. I provide further remarks in distinguishing spacetime superpositions that are genuinely quantum-gravitational, notably with reference to recent proposals to test gravitationally-induced entanglement, and those in which a putative superposition can be re-expressed in terms of dynamics on a single, fixed spacetime background.

### External references

- 23050123
- bb6528e8-0a8c-43f3-a943-bc801a510084
- 3005a389-2f1e-4f8d-823c-bb6f28e497cb