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

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When a polymer solution droplet is deposited on a lyophobic surface, the contact line is moved back to some degree and subsequently pinned. An experimental setup is constructed to investigate not only the receding process but also an internal flow of polystyrene-acetophenone and -anisole solutions. As a result, the time variation of the evaporation rate per unit area during receding does not strongly depend on the initial solute concentration. The average solute concentration at the pinning of the contact line increases as the initial solute concentration increases. A convective circulation flow that is upward at the axis of symmetry is observed. This flow pattern is different from those of pure liquids such as water, acetone, benzene, and so forth, which have been previously reported. Furthermore, the observed flow is enhanced as the initial solute concentration increases, contrary to an increase in the fluid viscosity. To resolve these discrepancies, the mechanism of the flow is numerically investigated using a hemispherical droplet model considering the density and surface tension distributions. The numerical results demonstrate that the circulation flow that is experimentally observed is actually caused. It is also found that the solutal Rayleigh effect initially induces the internal flow, and subsequently the solutal Marangoni effect dominates the flow. Both effects are enhanced as the initial concentration increases because of the evaporative mass balance at the free surface.

in Wiley InterScience (www.interscience.wiley.com).The factors determining the thin-film shape from an evaporating polymer solution droplet are experimentally studied. The polystyrene/xylene droplets, whose diameter is controlled in the range of 30-100 mm with the mass fraction of 0.5-3.0 wt % are ejected onto a lyophobic substrate. The droplet on the substrate results in an axisymmetric or nonaxisymmetric ring-like/dot-like film. The film configuration is dominated by the evaporation rate and the film symmetry is governed by the local pinning time at the periphery. Various relationships are also found among the evaporation rate, pinning time, wetting diameter, and average solute concentration of which the nondimensionalization pronounces explicit relationships and similarity.

Circular type' interferometric system for quantum key distribution is proposed. The system has naturally self-alignment and compensation of birefringence and also has enough efficiency against polarisation dependence. Moreover it is easily applicable to multi-party. Key creation with 0.1 photon per pulse at a rate of 1.2KHz with a 5.4% QBER over a 200m fiber was realized.

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A possible protective effect of coffee or caffeine intake in the formation of gallstones has been suggested in some epidemiological studies. We examined the relation of coffee, green tea, and caffeine intake to gallstone disease in middle-aged Japanese men, distinguishing known gallstones from unknown diagnosed gallstones. Study subjects were 174 cases of gallstones as determined by ultrasonography, 104 cases of postcholecystectomy, and 6889 controls of normal gallbladder in the total of 7637 men who received a health examination at four hospitals of the Self-Defense Forces (SDF). Of the 174 cases of prevalent gallstones, 50 had been aware of having gallstones. Previously diagnosed gallstones and postcholecystectomy were combined as known gallstone disease. The consumption of coffee and green tea was ascertained by a self-administered questionnaire, and caffeine intake was estimated. Statistical adjustment was done for body mass index, smoking, alcohol use, rank in the SDF, and hospital. Coffee and caffeine intake were associated each with a statistically significant increase in the prevalence odds of known gallstone disease, but unrelated to newly diagnosed gallstones. Adjusted odds ratios of known gallstone disease were 1.7 (95% confidence interval [CI] 1.1-2.8) for coffee consumption of five cups or more per day vs. no consumption and 2.2 (95% CI: 1.3-3.7) for caffeine intake of 300 mg/day or more vs. less than 100 mg/day. The consumption of green-tea showed no material association with either unknown gallstones or known gallstone disease. The findings do not support a hypothesis that coffee drinking may be protective against gallstone formation.

New quantum cryptography, often called Y-00 protocol, has much higher performance than the conventional quantum cryptographies. It seems that the conventional quantum cryptographic attacks are inefficient at Y-00 protocol as its security is based on the different grounds from that of the conventional ones. We have, then, tried to cryptoanalyze Y-00 protocol in the view of cryptographic communication system. As a result, it turns out that the security of Y-00 protocol is equivalent to that of classical stream cipher.PACS numbers: 03.67. Dd, 42.50.Lc, 42.50.Ar Quantum cryptography has appeared as a promising way to achieve security without depending on any computational complexity assumption. However, most of the proposed schemes up to date are based on single photon states (QCSPS) thus, presenting a well-known negative characteristic, namely, its bit rate is much slower than that of normal optical communication systems.Recently a quantum cryptography scheme which uses mesoscopic coherent states has been reported [1,2,3,4]. This scheme has much higher performance than conventional ones which are based on single photon states [5,6,7]. Because this scheme based on mesoscopic coherent states, often called "Y-00 protocol [8]," has an average photon number of 100-1,000 photons per pulse, its bit rate is expected to be 100-1,000 times faster than that of QCSPS. In addition, the required technical level to realize the protocol is supposed to be quite the same as in conventional optical systems. Y-00 protocol would be, then, a sufficiently fast and easily realizable quantum cryptography scheme, if it had actually perfect security.In this paper, we show that the Y-00 protocol does not provide perfect security, even against the simplest of cryptographic attacks, ciphertext-only ones. A usual cryptographic system consists of two channels ( Fig.1): an open channel for exchanging encrypted messages and a secure channel for key distribution. Quantum cryptography based protocols, including Y-00 protocol, provide a realization of the secure channel for key distribution. Let us underline that our attack targets are not only the secure channel, but also the open channel for messages.We also show that the security of Y-00 protocol is just equivalent to that of a classical stream cipher. In other words, we can safely say that Y-00 protocol has no perfect security and that its security depends on just a common computational complexity assumption, being then no better than currently used schemes. Y-00 protocol is a quantum key expansion (QKE) scheme. Both Alice and Bob must share a secret key K s in advance. Notice that, even conventional quantum cryptography can be regarded as quantum key expansion schemes, since a short key is needed for the authentication of the classical channel. Y-00 protocol uses the secret key for quantum modulation and de-modulation in a quantum channel for expansion of the key.Y-00 protocol has, then, 2M non-orthogonal coherent states called "qumodes" :where α ∈ C and k ∈ {0, . . . , 2M − 1}, orin the polar...