Coherence as a resource for $N$-box and quantum pigeonhole paradoxes

Abstract:Pre- and post-selection (PPS) paradoxes are striking demonstrations of quantum nonclassicality. Logical PPS paradoxes, where inferences made with the Aharonov-Bergmann-Lebowitz (ABL) rule are exactly 0 or 1, are linked to contextuality. Non-logical paradoxes lack this strong signature. In this work, we analyse more general, non-logical PPS scenarios involving mixed pre- and post-selected states. We show that two such scenarios, the $N$-box and quantum pigeonhole paradoxes, require coherence of both pre- and post-selected states in the basis of the intermediate measurement. This is done by showing each paradox holds if and only if there is weak-value anomaly for a single, paradox-specific operator, together with the fact that weak-value anomaly requires coherence. This clarifies the role of different notions of nonclassicality in these scenarios, highlighting the required quantitative departures from (strictly) classical explanations provided by incoherent sub-theories of quantum theory.

v1: 16 pages, 3 figures. Comments are welcome!

arXiv:2607.24282 [quant-ph]

(or arXiv:2607.24282v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2607.24282 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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