From the HPC Wire: "BBN Technologies announced that it has built the world's first quantum cryptography network and is now operating it continuously beneath the streets of Cambridge, Massachusetts. Today the DARPA Quantum Network links BBN's campus to Harvard University; soon it will stretch across town to include Boston University as a third link...
"Quantum cryptography, invented by Charles Bennett and Giles Brassard in the 1980s, prepares and transmits single photons of light, through either fiber optic cable or the atmosphere, to distribute cryptographic keys that are used to encrypt and decrypt messages. This method of securing information is radically different from methods based on mathematical complexity, relying instead on fundamental physical laws. Because very small (quantum) particles are changed by any observation or measurement, eavesdropping on a quantum cryptography system is always detectable.
"The DARPA Quantum Network has improved on these techniques to create a highly robust, six-node network that is both extremely secure and 100% compatible with today's Internet technology... 'People think of quantum cryptography as a distant possibility,' said Chip Elliott, a Principal Scientist at BBN and leader of its quantum engineering team, 'but the DARPA Quantum Network is up and running today...' "