Freiburg 2019 – wissenschaftliches Programm
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FM: Fall Meeting
FM 7: Secure Communication & Computation I
FM 7.7: Talk
Montag, 23. September 2019, 15:45–16:00, 1009
Bipartite and multipartite QKD via single-photon interference — •Federico Grasselli1, Álvaro Navarrete2, Marcos Curty2, Hermann Kampermann1, and Dagmar Bruss1 — 1Heinrich-Heine-Universität, Düsseldorf, Germany — 2Escuela de Ingenieria de Telecomunicación, University of Vigo, Spain
Twin-Field (TF) QKD has been proven to beat the point-to-point private capacity of a lossy quantum channel, thanks to performing single-photon interference in an untrusted node. We focus on the TF-QKD protocol introduced by Curty et al., whose security relies on the estimation of the detection statistics of Fock-states through the decoy-state method. We derive analytical bounds on these quantities assuming either two, three or four independent decoy intensity settings for each party, and we investigate the protocol's performance (arXiv:1902.10034). We show that two decoy intensity settings are enough to beat the point-to-point private capacity of the channel, that the protocol is fairly robust against uncorrelated intensity fluctuations of the optical pulses and that one can extract a secret key even when the losses in the two channels are highly asymmetric.
We then generalize the protocol to the multipartite scenario, by devising a conference key agreement (CKA) protocol where the users simultaneously distill a secret conference key through single-photon interference. The new CKA is better suited to high-loss scenarios than previous multipartite QKD schemes and employs for the first time a W-class state as its entanglement resource. We compare its performance with the iterative use of bipartite QKD protocols.