All you need is the universal correlation detector: A unified approach to universalize communication protocols over quantum channels

Abstract:Constructing optimal quantum information protocols without complete knowledge of the underlying states or channels is a central challenge. We address this challenge by developing universal correlation detection as a common building block for quantum communication. Our detectors distinguish a bipartite state from the product of its marginals and attain the same first-order asymptotic performance as optimal tests constructed with complete state information. For general bipartite quantum states, knowledge of a single marginal suffices: a detector depending only on that marginal is first-order optimal for every compatible state. For classical-quantum states, the detector is fully universal and requires no prior state information. By combining these detectors with position-based decoding and convex splitting, we construct channel-independent coding schemes that achieve capacity for a range of communication tasks. These results turn universal correlation detection into a systematic tool for universal protocol design, providing a unified route to designing capacity-achieving protocols for many communication tasks over unknown quantum channels.

arXiv:2609.29954 [quant-ph]

(or arXiv:2609.29954v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2609.29954 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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