Rostock 2019 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 45: Quantum Information (Quantum Communication) II

Q 45.7: Talk

Thursday, March 14, 2019, 12:00–12:15, S HS 002 Chemie

Device-independent quantum key distribution beyond CHSH violation — •Timo Holz, Sarnava Datta, Hermann Kampermann, and Dagmar Bruß — Institut für Theoretische Physik III, Heinrich-Heine-Universität Düsseldorf, D-40225 Düsseldorf, Germany

In early proposed protocols for quantum key distribution (QKD) one imposes in general too strong assumptions on the devices that reality cannot match. Any realistic implementation is imperfect, which can be exploited by a malicious eavesdropper. The strongest form of security is thus achieved by avoiding any assumption about the internal working of the devices, which is called device-independent (DI) QKD. Security proofs for DIQKD rely on a loophole-free violation of Bell inequalities. The violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality is directly connected to the DI secret-key rate [1]. We aim at generalizing this connection to the case of n parties, m measurement settings and k measurement outcomes. In particular, we establish a connection between the DI secret-key rate and the violation of a Bell inequality other than CHSH, by numerically lower bounding the secret-key rate via semidefinite programming, based on [2]. In principle, this numerical approach allows a calculation of lower bounds on the secret-key rate in terms of the violation of a general (n,m,k)-Bell inequality, which is constructed in a preceding step from the measurement data, cf. [3]. We illustrate our method with an example.

[1] A. Acin et al., Phys. Rev. Lett. 98, 230501 (2007)

[2] L. Masanes et al., Nat. Commun. 2, 238 (2011)

[3] J. Szangolies et al., Phys. Rev. Lett. 118, 260401 (2017)