Quantum Cryptography over Underground Optical Fibers

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light whose security is based on the inviolability of the laws of quantum mechanics. An adversary can neither successfully tap the key transmissions, nor evade detection, owing to Heisenberg’s uncertainty principle. In this paper we describe the theory of quantum cryptography, and the most recent results from our experimental system with which we are generating key material over 14km of underground optical fiber. These results demonstrate that opticalfiber based quantum cryptography could allow secure, real-time key generation over “open” multi-km node-to-node optical fiber communications links between secure “islands.”