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QI: Fachverband Quanteninformation

QI 14: Quantum Information Poster Session

QI 14.9: Poster

Mittwoch, 11. März 2026, 18:00–21:00, P4

Bounds on quantum conference key agreement in networks with bipartite links — •Justus Neumann, Anton Trushechkin, Hermann Kampermann, and Dagmar Bruß — Heinrich Heine Universität Düsseldorf

Quantum conference key agreement allows several users to establish a shared secret key. A common approach is to use multipartite entangled states like Greenberger-Horne-Zeilinger states, but these are difficult to create in real networks. We instead consider a more practical setting where only two-party entangled states are available between network nodes, and users can only perform local measurements followed by classical communication, without quantum memory. We study the general conference key agreement problem and derive a fundamental upper bound on the achievable key rate. We prove that, in any network composed only of bipartite sources, one cannot outperform a simple strategy: perform ordinary two-party quantum key distribution between one user and each of the others, and then merge the pairwise keys into a common conference key. This shows that complex multipartite strategies offer no rate advantage in such networks.

Keywords: quantum networks; quantum key distribution; conference key agreement