Maintenance-free wavelength-division-multiplexing quantum key distribution for 30 days was achieved through a 22-km field fiber. Using polarization-independent interferometers and stabilization techniques, we attained a quantum bit error rate as low as 1.70% and a key rate as high as 229.8 kbps, making the record of total secure key of 595.6 Gbits accumulated over an uninterrupted operation period. Tomita, "Efficient and low-noise single-photon avalanche photodiode for 1.244-GHz clocked quantum key disitribution," Opt. Express 19(21), 20531-20541 (2011). 12. K. Yoshino, T. Ochi, M. Fujiwara, A. Tomita, M. Sasaki, and A. Tajima, "Long-term field demonstration of WDM quantum key distribution system with stabilization control," Proc. CLEO-PR WG-2-1 (2013). 13. Y. Nambu, K. Yoshino, and A. Tomita, "Quantum encoder and decoder for practical quantum key distribution using a planar lightwave circuit," J. Mod. Opt. 55(12), 1953-1970 (2008 References and links

We present practical GHz-clocked QKD systems, next generation entanglement QKD technologies, and QKD platform to manage the secure keys and to support a variety of applications. We then show the intrinsic limit of QKD, i.e., a key rate bound, and discuss how to realize the provable (information theoretic) security with a larger secrecy capacity over longer distances. In particular, we present a basic theory of physical layer cryptography, which characterizes the secrecy capacity, and engineers the tradeoff between the efficiency of reliable transmission and secrecy of communication. We introduce a concept to unify these schemes in photonic network, referred to as quantum photonic network. Future issues for realizing this new network paradigm are discussed.Index Terms-Quantum communication, quantum cryptography, quantum key distribution, photonic network.

The fundamental architecture and functions of secure key management in a quantum key distribution (QKD) network with enhanced universal interfaces for smooth key sharing between arbitrary two nodes and enabling multiple secure communication applications are proposed. The proposed architecture consists of three layers: a quantum layer, key management layer and key supply layer. We explain the functions of each layer, the key formats in each layer and the key lifecycle for enabling a practical QKD network. A quantum key distribution-advanced encryption standard (QKD-AES) hybrid system and an encrypted smartphone system were developed as secure communication applications on our QKD network. The validity and usefulness of these systems were demonstrated on the Tokyo QKD Network testbed.

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