We study a novel protocol for reference frame independent (RFI) quantum key distribution (QKD) using six states for Alice and four states for Bob, while previous RFI protocols require a six state analyzer for Bob. Our protocol can generate a secure key for any possible phase of the entangled state, provided the variation is small compared to the measurement rate, shown by our numerical key rate analysis. We perform a proof-of-principle experiment using polarization entangled photon pairs. In the presence of a varying rotational phase, we obtain a consistently low error rate of less than 4% indicating the feasibility of this protocol for QKD. Our protocol is hence beneficial but not limited to applications in satellite or mobile free-space QKD, where a communication node must limit resources and restrict the number of measured states to four instead of six.
@article{arxiv.1905.09197,
title = {Demonstration of a 6 State-4 State Reference Frame Independent channel for Quantum Key Distribution},
author = {Ramy Tannous and Zhangdong Ye and Jeongwan Jin and Katanya B. Kuntz and Norbert Lütkenhaus and Thomas Jennewein},
journal= {arXiv preprint arXiv:1905.09197},
year = {2019}
}