Decoupling by local random unitaries without simultaneous smoothing, and applications to multi-user quantum information tasks.

Seminar author:Pau Colomer Saus

Event date and time:07/27/2023 04:00:pm

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Decoupling is a fundamental primitive in the design of quantum transmission codes, quantum Slepian-Wolf coding, cryptographic communication, and channel simulation, but has so far been largely limited to single-user settings. Recently, we demonstrated how to leverage tensorization properties of expected-contractive maps, to extend the basic toolbox to simultaneous decoupling in a multipartite setting where each party applies their own random unitary. We have successfully established achievability bounds for general multipartite decoupling, using the usual smooth conditional min-entropies in one-shot scenarios, as well as conditional Rényi entropies. We have shown the power of these results by presenting a series of relevant applications in multi-user quantum information tasks.