13,685 research outputs found

    Polarity of liquid mixtures with components of limited miscibility

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    Binary mixtures of organic solvents with limited miscibility are investigated by a two parameter equation which reliably describes the polarity of mixtures as a function of their composition. A relation is found between limited miscibility and critical change of solvent structure

    Bond-Bending and Bond-Stretching Phonons in Ferromagnetic La_0.7Sr_0.3MnO_3

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    Longitudinal optical phonons with oxygen character were measured in La_0.7Sr_0.3MnO_3 by inelastic neutron scattering in the (1 0 0) cubic direction and results were compared with shell model predictions. Measurements were performed in several Brillouin zones, which enabled us to identify the eigenvectors independent of the shell model. All major disagreements between model predictions and experimental results are primarily due to the anomalous downward dispersion of the bond-stretching vibration. The main new result is that the rhombohedral distortion of the cubic lattice makes the bond-stretching vibrations interact strongly with bond-bending modes folded into the cubic Brillouin zone

    Postselection threshold against biased noise

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    The highest current estimates for the amount of noise a quantum computer can tolerate are based on fault-tolerance schemes relying heavily on postselecting on no detected errors. However, there has been no proof that these schemes give even a positive tolerable noise threshold. A technique to prove a positive threshold, for probabilistic noise models, is presented. The main idea is to maintain strong control over the distribution of errors in the quantum state at all times. This distribution has correlations which conceivably could grow out of control with postselection. But in fact, the error distribution can be written as a mixture of nearby distributions each satisfying strong independence properties, so there are no correlations for postselection to amplify.Comment: 13 pages, FOCS 2006; conference versio

    Trends of Developments in the Information Systems of the Soviet Union and the Comecon Countries

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    Ab initio calculation of the GG peak intensity of graphene: Combined study of the laser and Fermi energy dependence and importance of quantum interference effects

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    We present the results of a diagrammatic, fully ab initio calculation of the GG peak intensity of graphene. The flexibility and generality of our approach enables us to go beyond the previous analytical calculations in the low-energy regime. We study the laser and Fermi energy dependence of the GG peak intensity and analyze the contributions from resonant and non-resonant electronic transitions. In particular, we explicitly demonstrate the importance of quantum interference and non-resonant states for the GG peak process. Our method of analysis and computational concept is completely general and can easily be applied to study other materials as well.Comment: 10 pages, 5 figure
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