One of the obstacles to deployment of QKD solutions has been the distance limitation. Solutions using relays have been proposed but these rely on link-by-link key establishment. We present a new technique to extend the distance of a quantum key distribution channel using an active relay. Each relay acts as an intercept/resend device and allows the establishment of an end-to-end key. It has been argued that such relays cannot be used to extend the distance, but we show that with a suitable adaptation of the protocol the effective key distribution distance can be increased.
@article{arxiv.1203.0628,
title = {Extending the Reach of QKD Using Relays},
author = {Stephen M. Barnett and Simon J. D. Phoenix},
journal= {arXiv preprint arXiv:1203.0628},
year = {2016}
}