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arXiv · 2608.04099

Contextuality in Sequential State Discrimination

Nyan Raess·Farid Shahandeh
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Abstract

Generalized contextuality is known to be required in optimal strategies for quantum state discrimination protocols. More recently, sequential discrimination tasks have been studied; n players attempt to determine in which state a qubit was prepared, in such a way that they all have a finite probability of success. We consider the extent to which contextuality plays a role in sequential versions of both unambiguous and minimum error discrimination. In the standard nonsequential case where n = 1, we use the COPE formalism to demonstrate that the presence of contextuality is guaranteed not only for the optimal measurement, but for a specific set of nonoptimal measurements as well. In the sequential case n > 1, we show that the presence of contextuality depends on which states are prepared, and on the protocol (unambiguous or minimum error) selected.

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Nyan Raess, Farid Shahandeh. 2026-08-04. Contextuality in Sequential State Discrimination. https://arxiv.org/abs/2608.04099

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