The discrete variables (DV) time-frequency (TF) quantum key distribution (QKD) protocol is a BB84 like protocol, which utilizes time and frequency as complementary bases. As orthogonal modulations, pulse position modulation (PPM) and frequency shift keying (FSK) are capable of transmitting several bits per symbol, i.e. per photon. However, unlike traditional binary polarization shift keying, PPM and FSK do not allow perfectly complementary bases. So information is not completely deleted when the wrong-basis filters are applied. Since a general security proof does not yet exist, we numerically assess DV-TF-QKD. We show that the secret key rate increases with a higher number of symbols per basis. Further we identify the optimal pulse relations in the two bases in terms of key rate and resistance against eavesdropping attacks.
@article{arxiv.1705.04580,
title = {Numerical Assessment and Optimization of Discrete-Variable Time-Frequency Quantum Key Distribution},
author = {Jasper Rödiger and Nicolas Perlot and Roberto Mottola and Robert Elschner and Carl-Michael Weinert and Oliver Benson and Ronald Freund},
journal= {arXiv preprint arXiv:1705.04580},
year = {2017}
}