Black Holes Decohere Quantum Superpositions

Abstract

We show that if a massive body is put in a quantum superposition of spatially separated states, the mere presence of a black hole in the vicinity of the body will eventually destroy the coherence of the superposition. This occurs because, in effect, the gravitational field of the body radiates soft gravitons into the black hole, allowing the black hole to acquire "which path" information about the superposition. A similar effect occurs for quantum superpositions of electrically charged bodies. We provide estimates of the decoherence time for such quantum superpositions. We believe that the fact that a black hole will eventually decohere any quantum superposition may be of fundamental significance for our understanding of the nature of black holes in a quantum theory of gravity.

arXiv comment10 pages. Third prize essay in the Gravity Research Foundation 2022 Essays on Gravitation. Minor editorial changes in v2

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• Information Loss
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• An electromagnetic analog of gravitational wave memory
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Cited by in corpus (4)

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• Phenomenology of Holography via Quantum Coherence on Causal Horizons