Experimental quantum key distribution without monitoring signal disturbance

TL;DR

This paper reports the first experimental implementation of a quantum key distribution protocol that generates secure keys without monitoring measurement outcome disturbances, using a novel RRDPS protocol over 30 km fiber.

Contribution

It demonstrates a practical realization of the RRDPS protocol, eliminating the need for disturbance monitoring in QKD, and achieves key distribution over 30 km fiber.

Findings

Successful key distribution over 30 km fiber

First experimental realization of RRDPS protocol without disturbance monitoring

Demonstrates practical feasibility of disturbance-free QKD

Abstract

Since the invention of Bennett-Brassard 1984 (BB84) protocol, many quantum key distribution (QKD) protocols have been proposed and some protocols are operated even in field environments. One of the striking features of QKD is that QKD protocols are provably secure unlike cryptography based on computational complexity assumptions. It has been believed that, to guarantee the security of QKD, Alice and Bob have to monitor the statistics of the measurement outcomes which are used to determine the amount of the privacy amplification to generate a key. Recently a new type of QKD protocol, called round robin differential phase shift (RRDPS) protocol, was proposed, and remarkably this protocol can generate a key without monitoring any statistics of the measurement outcomes. Here we report an experimental realization of the RRDPS protocol. We used a setup in which Bob randomly chooses one from four interferometers with different pulse delays so that he could implement phase difference measurements for all possible combinations with five-pulse time-bin states. Using the setup, we successfully distributed keys over 30 km of fiber, making this the first QKD experiment that does not rely on signal disturbance monitoring.