Quantum Theory Can Decohere from a Causally-Indefinite Post-Quantum Theory

• URL: http://arxiv.org/abs/2511.02772v1
• Date: Tue, 04 Nov 2025 17:58:47 GMT
• Title: Quantum Theory Can Decohere from a Causally-Indefinite Post-Quantum Theory
• Authors: James Hefford, Matt Wilson,
• Abstract summary: We find a process satisfying the axioms of hyper-decoherence which produces standard quantum theory from the theory of quantum boxes.<n>This hyper-decoherence map evades the no-go theorem of Lee and Selby by relaxing constraints on signalling to the past.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: We find a process satisfying the axioms of hyper-decoherence which produces standard quantum theory from the theory of quantum boxes (higher-order quantum theory with the non-signalling tensor product). This hyper-decoherence map evades the no-go theorem of Lee and Selby by relaxing constraints on signalling to the past and the uniqueness of purifications. We discuss some natural opposing conclusions: that the existence of this map might be evidence of a genuine hyper-decoherence process producing causal quantum theory from its causally-indefinite higher-order theory; or that it serves as an indication that the axioms of hyper-decoherence might need careful re-consideration, especially regarding the subtle albeit central role that purity plays.

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