Quantum key distribution shares fiber with live data

Toshiba Research Europe, BT Group, ADVA Optical Networking, and the National Physical Laboratory (NPL), the UK’s national measurement institute, have carried out what they claim is the first successful trial of quantum key distribution (QKD) technology over a live fiber-optic network.

The trial, which was supported by the UK’s Technology Strategy Board, is also the first to use a single lit optical fiber to transmit both the data and the quantum key itself. The use of a single fiber is significant, the researchers say, as both the quantum key and the encrypted data can now use the same pathway for the first time. Previously, two or three fibers were needed to deliver a secure connection.

The trial paves the way for further development and research into practical applications for the technology, the companies say.

Dr. Tim Whitley, managing director of research and innovation at BT, said, “Quantum key distribution is an exciting new frontier in security technology. Through collaboration with Toshiba, ADVA Optical Networking, and NPL, we’re helping to push the boundaries of what is currently possible and opening up new possibilities for this technology to be used more widely in the future.”

Providing an additional layer of security over and above standard methods used by banks and credit card companies to send data encryption keys across a network, QKD shares a key between two users that is made completely secure using the physical mechanisms of quantum mechanics (see “The security of networks and the role optical can play in it”).

By transmitting the information in a quantum state, any attempt to intercept the key can be identified, as it introduces anomalies which can be detected. If this occurs, the transaction can be aborted, and a new key sent automatically. By sending multiple quantum keys every second, the security of a fiber-optic line can be constantly monitored and attempts to tap the signal can be instantly identified.

The test was conducted using quantum equipment developed by Toshiba, measured and evaluated by the Quantum Detection Group at NPL, and running in conjunction with ADVA Optical Networking’s encryption equipment over a live BT fiber link between Adastral Park, BT’s technology research campus in Suffolk, and another BT site in Ipswich.

Andrew Shields from Toshiba Research Europe in Cambridge, said, “The first field trial of QKD on lit fiber marks an importance advance for the technology. Using techniques to filter out noise from the very weak quantum signals, we’ve shown that QKD can be operated on optical fibers installed in the ground and carrying conventional data signals. This means QKD can be implemented without the need for additional ‘dark fiber’ that is often unavailable or prohibitively expensive.”

The QKD system works by sending a known amount of photons across the optical fiber. Knowing the number of photons sent and received is integral to the security of the system. Alastair Sinclair from NPL, explained, “At NPL, we’ve developed a series of measurements that are sensitive enough to detect the individual particles of light, which we are using to independently verify the security of the system, in order to improve customer confidence and overcome one of the major barriers to market.”

The partners say the trial paves the way for more advanced research into QKD.

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