Abstract:A secure communication network with quantum key distribution in a metropolitan area is reported. Six different QKD systems are integrated into a mesh-type network. GHz-clocked QKD links enable us to demonstrate the world-first secure TV conferencing over a distance of 45km. The network includes a commercial QKD product for long-term stable operation, and application interface to secure mobile phones. Detection of an eavesdropper, rerouting into a secure path, and key relay via trusted nodes are demonstrated in this network. ©2011 Optical Society of AmericaOCIS codes: (270.5568) Quantum cryptography; (060.5565) Quantum communications. References and links1. N. Gisin, G. Ribordy, W. Tittel, and H. Zbinden, "Quantum cryptography," Rev. Mod. Phys. 74(1), 145-195 (2002). 2. V. Scarani, H. Bechmann-Pasquinucci, N. J. Cerf, M. Dušek, N. N. Lütkenhaus, and M. Peev, "The security of practical quantum key distribution," Rev. Mod. Phys. 81(3), 1301-1350 (2009

We found that self-determining collimated light is generated in a photonic crystal fabricated on silicon. The divergence of the collimated beam is insensitive to that of the incident beam and much smaller than the divergence that would be generated in conventional Gaussian optics. The incident-angle dependence of the self-collimated light propagation including lens-like divergent propagation was interpreted in terms of the highly modulated dispersion surfaces with inflection points, where the curvature changes from downward to upward corresponding to respectively a concave/convex-lens case. This demonstration is an important step towards controlling beam profile in photonic crystal integrated light circuits and towards developing “photonic crystalline optics.”

An attempt was made to prepare porous carbon by using the channels of Y zeolite as a template. Poly(acrylonitrile) and poly(furfuryl alcohol) were carbonized in the zeolite channels and the resultant carbon/zeolite complexes were subjected to acid treatment in order to extract carbon from the zeolite framework. In addition, pyrolytic carbon deposition in the channels was carried out by exposing the zeolite to propylene at high temperature, and then the carbon was liberated in the same manner as above. The morphology and structure of the carbon prepared in the channels were characterized, and the results were discussed in relation to the morphology and structure of the original zeolite template. It was found that the microscopic morphology of the resultant carbons reflects that of the corresponding zeolites. All of these carbons are highly porous, and some of the CVD carbons have BET surface areas as high as >2000 m 2 /g.

Quantum optical Gaussian states are a type of important robust quantum states which are manipulatable by the existing technologies. So far, most of the important quantum information experiments are done with such states, including bright Gaussian light and weak Gaussian light. Extending the existing results of quantum information with discrete quantum states to the case of continuous variable quantum states is an interesting theoretical job. The quantum Gaussian states play a central role in such a case. We review the properties and applications of Gaussian states in quantum information with emphasis on the fundamental concepts, the calculation techniques and the effects of imperfections of the real-life experimental setups. Topics here include the elementary properties of Gaussian states and relevant quantum information device, entanglement-based quantum tasks such as quantum teleportation, quantum cryptography with weak and strong Gaussian states and the quantum channel capacity, mathematical theory of quantum entanglement and state estimation for Gaussian states.

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