Quantum circuit for security proof of quantum key distribution without encryption of error syndrome and noisy processing

One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in classical postprocessing, i.e., the syndrome for the error-correction step has to be encrypted. In this paper, we remove this limitation by constructing a quantum circuit for the virtual protocol. Moreover, our circuit with a shield system gives an intuitive proof of why adding noise to the sifted key increases the bit error rate threshold in the general case in which one of the parties does not possess a qubit. Thus, our circuit bridges the simple proof and the use of wider classes of classical postprocessing.Comment: 8 pages, 2 figures. Typo correcte

Photophysical Characterization and BSA Interaction of Direct Ring Carboxy Functionalized Symmetrical squaraine Dyes

A series of far-red sensitive symmetrical squaraine dyes bearing direct –COOH functionalized indole ring were synthesized, characterized and subjected to photophysical investigations. These symmetrical squaraine dyes were then subjected to investigate their interaction with bovine serum albumin (BSA) in Phosphate buffer solutions. All the squaraine dyes under investigation exhibit intense and sharp optical absorption mainly in the far-red wavelength region from 550 nm -700 nm having very high molar extinction coefficients from 1.3 × 105 dm3.mol−1.cm−1. A very small Stokes shift of 10-17 nm indicates the rigid conformational structure of squaraine chromophore. Interaction of these dyes with BSA leads to not only enhanced emission intensity but also bathochromically shifted absorption maximum due to formation of dye-BSA conjugate. These dyes bind strongly with BSA having about an order of magnitude higher binding constant as compared to the reported squaraine dyes. Amongst the symmetrical squaraine dyes investigated in this work one bearing substituents like trifluorobutyl as alkyl chain at N-position of indole ring and carboxylic acid on benzene ring at the terminal (SQ-26) exhibited highest association with the BSA having very high binding constant 8.01 × 106 M−1.12th International Conference on Nanomolecular Electronics (ICNME-2016), December 14-16, 2016, Kobe International Conference Center, Kobe, Japa

Security of quantum key distribution with iterative sifting

Several quantum key distribution (QKD) protocols employ iterative sifting. After each quantum transmission round, Alice and Bob disclose part of their setting information (including their basis choices) for the detected signals. The quantum phase of the protocol then ends when the numbers of detected signals per basis exceed certain pre-agreed threshold values. Recently, however, Pfister et al. [New J. Phys. 18 053001 (2016)] showed that iterative sifting makes QKD insecure, especially in the finite key regime, if the parameter estimation for privacy amplification uses the random sampling theory. This implies that a number of existing finite key security proofs could be flawed and cannot guarantee security. Here, we solve this serious problem by showing that the use of Azuma's inequality for parameter estimation makes QKD with iterative sifting secure again. This means that the existing protocols whose security proof employs this inequality remain secure even if they employ iterative sifting. Also, our results highlight a fundamental difference between the random sampling theorem and Azuma's inequality in proving security.Comment: 9 pages. We have found a flaw in the first version, which we have corrected in the revised versio

Adaptive radiation of gobies in the interstitial habitats of gravel beaches accompanied by body elongation and excessive vertebral segmentation

<p>Abstract</p> <p>Background</p> <p>The seacoasts of the Japanese Arc are fringed by many gravel beaches owing to active tectonic uplift and intense denudation caused by heavy rainfall. These gravel beaches are inhabited by gobies of the genus <it>Luciogobius </it>that burrow into the gravel sediment and live interstitially. Although their habitat and morphology (<it>e. g</it>., reduced fins, elongated, scale-less body, and highly segmented vertebral column) are highly unusual among fishes, little is known on how their morphological evolution has facilitated the colonization of interstitial habitats and promoted extensive diversification. We conducted thorough sampling of <it>Luciogobius </it>and related species throughout Japan, and performed molecular phylogenetic analysis to explore the patterns of morphological evolution associated with gravel beach colonization.</p> <p>Results</p> <p>An analysis of the mitochondrial <it>cytochrome b </it>gene suggested a remarkable diversity of previously unrecognized species. The species-level phylogeny based on six protein-coding nuclear genes clearly indicated that interstitial species cluster into two distinct clades, and that transitions from benthic or demersal habits to interstitial habits are strongly correlated with an increase in vertebral number. Colonization of gravel beach habitats is estimated to have occurred ca. 10 Ma, which coincides with the period of active orogenesis of the Japanese landmass. Different species of interstitial <it>Luciogobius </it>inhabit sediments with different granulometric properties, suggesting that microhabitat partitioning has been an important mechanism facilitating speciation in these fishes.</p> <p>Conclusion</p> <p>This is the first study to document the adaptation to interstitial habitats by a vertebrate. Body elongation and excessive vertebral segmentation had been the key aspects enhancing body flexibility and fishes' ability to burrow into the gravel sediment. The rich diversity of coastal gravel habitats of the Japanese Arc has likely promoted the adaptive radiation of these unique gravel-dwelling fishes.</p

Fluorescence Energy Transfer in Dendritic Poly(L-lysine)s Combining Thirty-two Free Base- and Zinc(II)-porphyrins in Scramble Fashion

Dendritic poly(L-lysine)s combining thirty-two free base- and Zn(II)-porphyrins in scramble fashion were successfully synthesized and exhibited highly efficient (85%) fluorescence energy transfer from Zn(II)-porphyrins to free base-porphyrins

Quantum key distribution with correlated sources

Implementation security is a critical problem in quantum key distribution (QKD). With the advent of measurement-device-independent QKD, all security loopholes of the measurement unit have been closed. Securing the source, however, remains an elusive issue. Despite the tremendous progress made by developing security proofs that accommodate most typical source imperfections, such proofs usually disregard the effect of pulse correlations. That is, they disregard the fact that the state of an emitted signal can depend on the signals selected previously. Here, we close this gap by introducing a simple yet general method to prove the security of QKD with arbitrary pulse correlations. Our method is compatible with those security proofs that accommodate all the other source imperfections, thus paving the way towards achieving implementation security in QKD with arbitrary flawed devices. Moreover, we introduce a new security proof, which we call the reference technique, that provides high performance in the presence of source imperfections.Comment: This arXiv version contains some errata, please refer to the published paper for the correct versio

Aniline-Hydroxylation Activity of a Flavin-linked βαβα-Type Polypeptide Packing an Iron Porphyrin

Polypeptide containing iron porphyrin and flavin showed aniline-hydroxylation activity in the presence of 1-benzyl-1,4-dihydronicotinamide and O2. The increased activity at pH 5.5 compared with that at pH 7.0 suggests that the dissociation of His from the iron porphyrin favored the hydroxylation