Extending the Reach of QKD Using Relays

TL;DR

This paper introduces an active relay technique to extend the distance of quantum key distribution channels, overcoming previous limitations by adapting the protocol for end-to-end key establishment.

Contribution

It presents a novel protocol adaptation that enables relays to extend QKD distance, challenging prior assumptions about relay limitations.

Findings

Active relays can be used to extend QKD distance with protocol adaptation

End-to-end key establishment is achievable via intercept/resend relays

The proposed method surpasses previous link-by-link limitations

Abstract

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.