Adjustable round-pulse time delayer for round-robin differential phase-shift quantum key distribution

Abstract

Round-robin differential phase-shift (RRDPS) is one of the most promising quantum key distribution (QKD) protocol. Because cutting off the link between phase error and bit error and needing not of monitor the signal disturbance, the RRDPS protocol is in principle highly robust against channel disturbance for a large pulse packet size L and provides a new route towards QKD over long distances. However, once the experimental system is set up, the value of L is fixed. It cannot choose an optimal L to maximize the final key rate. In this paper, we propose a round-pulse time delayer, which can effectively realize the adjustable and a wide range of delay selection. This round-pulse time delayer has the advantages of simple structure and stable performance, which ensures the wide application for RRDPS-QKD protocol.