Experimental demonstration of counterfactual quantum key distribution

TL;DR

This paper experimentally demonstrates counterfactual quantum key distribution over a 12.5 km channel, showing its advantages in security against eavesdropping and specific quantum attacks using a high-visibility interferometer.

Contribution

It provides the first practical implementation of counterfactual quantum key distribution with high fringe visibility and security against common quantum attacks.

Findings

Achieved secure key distribution over 12.5 km channel

High fringe visibility of 96.4% in the interferometer

Secure against vacuum and passive photon-number-splitting attacks

Abstract

Counterfactual quantum key distribution provides natural advantage against the eavesdropping on the actual signal particles. It can prevent the photon-number-splitting attack when a weak coherent light source is used for the practical implementation. We realized the counterfactual quantum key distribution in an unbalanced Mach-Zehnder interferometer of 12.5-km-long quantum channel with a high-fringe visibility of 96:4%. As a result, we obtained secure keys against the noise-induced attack (eg. the vacuum attack) and passive photon-number-splitting attack.