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Q: Fachverband Quantenoptik und Photonik

Q 39: Posters: Quantum Optics and Photonics III

Q 39.41: Poster

Mittwoch, 11. März 2020, 16:30–18:30, Empore Lichthof

Tight bound on the eavesdropper's information in a multipartite device-independent scenario — •Federico Grasselli, Glaucia Murta, Hermann Kampermann, and Dagmar Bruß — Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, Düsseldorf, Germany

The security of device-independent (DI) quantum key distribution (QKD) holds independently of the actual functioning of the quantum devices and is based on the observation of a Bell inequality violation. In the seminal work by Pironio et al. [New J. Phys. 11, 045021 (2009)], the authors derive a tight bound on the eavesdropper's information which only depends on the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality observed by two parties. In a DI conference key agreement (CKA), the goal is to establish a conference key among several users by relying on a multipartite Bell inequality violation. So far, the security of such protocols either adapts the result of Pironio et al. (tightness not being guaranteed) or relies on loose numerical procedures (Navasqués-Pironio-Acin hierarchy). In this work, we obtain a tight bound on the eavesdropper's information when three parties observe a violation of the Mermin-Ardehali-Belinskii-Klyshko (MABK) inequality. The bound and its derivation can find applications in DICKA protocols. In order to obtain it, we also derive an analytical bound on the maximal violation of the MABK inequality achieved by an arbitrary three-qubit state.