Robust hierarchical metropolitan quantum cryptography network
of QKD system. Several field demonstrations of KLQI group including Beijing-Tianjin QKD experiment (2004), four-port star type network in Beijing (2007), and the Wuhu quantum cryptography network for Government administration (2009) clearly show that the stability and robustness of this QKD basic device are sufficient for practical implementations.
Networking is a milestone for the popularization of quantum cryptography service. The no-clone theorem of quantum system, however, makes data traffic difficult to route in the net while guaranteeing the security of the protocol. The Wuhu cryptography network assembles the widely used techniques of quantum router, active optical switch routing, and trusted relay to construct a hierarchical and extendable structure. A full-mesh backbone network is built with a quantum router in the center to supply a no-congestion communication between all the gateways simultaneously, while the quantum switch based on the time multiplexing can achieve a balance for subnets between network efficiency and speed. In addition, trusted relay is a compromising method to extend the scale of the network as long as a practical quantum repeater is still missing. The whole implement of this hierarchical framework is a big step toward the actualization of practical large-scale quantum cryptography network.
How to implement quantum cryptography in a practical utility is an important issue. As a solution to the basic question to distribute secure key in the classical cryptography, quantum cryptography and quantum key distribution have good prospects in the Internet and communication network for secure telephony, confidential fax and VPN, etc. We may also look at the Wuhu cryptography network as a creative and interesting attempt at electronic administration. Massive data traffic of government confidential files and personal information are entitled to the better protection offered by quantum cryptography. In the future, quantum cryptography will spread to secure media communication with instant video, sound, and text messages.
The Chinese researchers say that they share the ultimate goal of all security researchers to thwart hackers and Trojan horses. “Quantum cryptography as the earliest utility of quantum mechanism can supply an unconditional secure communication to benefit people,” they write. In practical implementation, “QKD scheme’s stability and key rate are not the only two important issues. Especially with the urgent and growing demand of emergent quantum cryptographic service, networking and routing techniques should be taken into serious consideration, as well as the application mode of QCN.”
The hierarchical metropolitan QCN field in Wuhu can serve not only public secure communication with QKD, but also act as a test bed to research those problems in realizations and applications of QCN in depth.
-read more in Fang-xing Xu, et al., “Field Experiment on a Robust Hierarchical Metropolitan Quantum Cryptography Network,” Chinese Science Bulletin 54, no. 17 (30 August 2009): 2991-97 (doi: 10.1007/s11434-009-0526-3)
