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arXiv · 2205.05033

Multipartite channel assemblages

Michał Banacki·Ravishankar Ramanathan·Paweł Horodecki
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Abstract

Motivated by the recent studies on post-quantum steering, we generalize the notion of bipartite channel steering by introducing the concept of multipartite no-signaling channel assemblages. We first show that beyond the bipartite case, the no-signaling and quantum descriptions of channel assemblages do not coincide. Using the Choi-Jamio{\l}kowski isomorphism, we present a complete characterization of these classes of assemblages and use this characterization to provide sufficient conditions for extremality of quantum channel assemblages within the set of all no-signaling channel assemblages. Finally, we introduce and discuss a relaxed version of channel steering where only certain subsystems obey the no-signaling constraints. In this latter asymmetric scenario we show the possibility of certifying a perfect key bit that is secure against a general no-signaling eavesdropper.

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Michał Banacki, Ravishankar Ramanathan, Paweł Horodecki. 2022-05-10. Multipartite channel assemblages. https://arxiv.org/abs/2205.05033

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