Schrödinger's Black Hole Cat

Abstract

In the absence of a fully-fledged theory of quantum gravity, we propose a "bottom-up" framework for exploring quantum-gravitational physics by pairing two of the most fundamental concepts of quantum theory and general relativity, namely quantum superposition and spacetime. We show how to describe such "spacetime superpositions" and explore effects they induce upon quantum matter. Our approach capitalizes on standard tools of quantum field theory in curved space, and allows us to calculate physical observables like transition probabilities for a particle detector residing in curvature-superposed de Sitter spacetime, or outside a mass-superposed black hole. Crucially, such scenarios represent genuine quantum superpositions of spacetimes, in contrast with superpositions of metrics which only differ by a coordinate transformation and thus are not different according to general relativity.

12 pages, Honourable Mention in the Gravity Research Foundation 2022 Awards for Essays on Gravitation

References in corpus (8)

• A Spin Entanglement Witness for Quantum Gravity
• Gravitationally-induced entanglement between two massive particles is sufficient evidence of quantum effects in gravity
• Static, stationary and inertial Unruh-DeWitt detectors on the BTZ black hole
• Improving resilience of the Quantum Gravity Induced Entanglement of Masses (QGEM) to decoherence using 3 superpositions
• Unruh-DeWitt detector response along static and circular geodesic trajectories for Schwarzschild-AdS black holes
• Entanglement amplification between superposed detectors in flat and curved spacetimes
• Jacob Bekenstein's Universes: From Black Holes to Modified Theories of Gravity
• Over the horizon: distinguishing the Schwarzschild spacetime and the ${\mathbb{RP}}^3$ spacetime using an Unruh-DeWitt detector

Cited by in corpus (6)

• Quantum superpositions of Minkowski spacetime
• Quantum Reference Frames at the Boundary of Spacetime
• Identification is Pointless: Quantum Coordinates, Localisation of Events, and the Quantum Hole Argument
• Entanglement harvesting in quantum superposed spacetime
• Quantum conformal symmetries for spacetimes in superposition
• Accelerated detector in a superposed spacetime