Quantum cryptography achieves ‘uncrackable’ communication networks

The researchers have succeeded in demonstrating continuous operation of quantum key distribution (QKD) with a secure bit rate exceeding 1Megabit/sec over 50Km of fibre for the first time. Averaged over a 24 hour period, the team claims that this is up to 1000 times higher than anything reported previously for a 50Km link. It was achieved using two innovations developed by the Cambridge team - a light detector for high bit rates and a feedback system, which is said to maintain a high bit rate at all times and requires no manual set up or adjustment. According to the Cambridge Lab, the research will enable the everyday use of 'one time pad' encryption. This application utilises one time pad encryption and requires the transmission of very long secret keys – the same length as the data itself. For this reason it has traditionally been used for short messages in situations requiring very high security. Dr Andrew Shields, who directs the research at Toshiba Research Europe said: "Although the feasibility of QKD with megabits per second has been shown in the lab, these experiments lasted only minutes or even seconds at a time and required manual adjustments. To the best of our knowledge this is the first time that continuous operation has been demonstrated at high bit rates. Although much development work remains this advance could allow unconditionally secure communication with significant bandwidths." Toshiba now plans to install a QKD technology demonstrator at the National Institute of Information and Communications Technology in Tokyo.