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.
@article{arxiv.1003.4621,
title = {Experimental demonstration of counterfactual quantum key distribution},
author = {Min Ren and Guang Wu and E Wu and Heping Zeng},
journal= {arXiv preprint arXiv:1003.4621},
year = {2015}
}