We present a quantum key distribution protocol based on four-level particles entanglement. Furthermore, a controlled quantum key distribution protocol is proposed by utilizing three four-level particles. We show that the two protocols are secure.
@article{arxiv.1002.1978,
title = {Quantum Key Distribution by Utilizing Four-Level Particles},
author = {Tao Yan and Fengli Yan},
journal= {arXiv preprint arXiv:1002.1978},
year = {2011}
}