Fast gates for ion traps by splitting laser pulses

We present a fast phase gate scheme that is experimentally achievable and has an operation time more than two orders of magnitude faster than current experimental schemes for low numbers of pulses. The gate time improves with the number of pulses following an inverse power law. Unlike implemented schemes which excite precise motional sidebands, thus limiting the gate timescale, our scheme excites multiple motional states using discrete ultra-fast pulses.We use beam-splitters to divide pulses into smaller components to overcome limitations due to the finite laser pulse repetition rate. This provides gate times faster than proposed theoretical schemes when we optimize a practical setup

Nonextensivity in the Solar Neighborhood

In the present study, we analyze the radial velocity distribution as a function of different stellar parameters such as stellar age, mass, rotational velocity and distance to the Sun for a sample of 6781 single low--mass field dwarf stars, located in the solar neighborhood. We show that the radial velocity distributions are best fitted by $q$--Gaussians that arise within the Tsallis nonextensive statistics. The obtained distributions cannot be described by the standard Gaussian that emerges within Boltzmann-Gibbs (B--G) statistical mechanics. The results point to the existence of a hierarchical structure in phase space, in contrast to the uniformly occupied phase space of B--G statistical mechanics, driven by the $q$--Central Limit Theorem, consistent with nonextensive statistical mechanics.Comment: 5 pages, 4 figures: EPL accepte

Improved semiclassical density matrix: taming caustics

We present a simple method to deal with caustics in the semiclassical approximation to the thermal density matrix of a particle moving on the line. For simplicity, only its diagonal elements are considered. The only ingredient we require is the knowledge of the extrema of the Euclidean action. The procedure makes use of complex trajectories, and is applied to the quartic double-well potential.Comment: 20 pages, 7 figures. Revised version, accepted for publication in Phys. Rev.

Avaliação da produtividade de girassol semado em dezembro em Uruguaiana-RS.

Com o objetivo de avaliar a produtividade de girassol em Uruguaiana-RS, foi realizado um experimento com semeadura em dezembro de 2010, conduzido na área experimental da FEPAGRO Fronteira Oeste, com delineamento experimental em blocos casualizados com quatro repetições. Foram avaliados os genótipos: BRS 321, BRS 323, Helio 358 e M734. A produtividade média do experimento foi de 2.043 kg.ha-1 . Quanto a variável número de dias para maturação fisiológica (NDF) os genótipos apresentaram comportamentos distintos sendo o mais tardio o M734 com 102 dias e o mais precoce o BRS 321 com 84 dias. The objective of this study was to evaluate grain yield of sunflower at Uruguaiana-RS,in an experiment sowed in December of 2010. It was carried out at FEPAGRO Fronteira Oeste field, in completely randomized blocks, with four replications. The genotypes evaluated were: BRS 321, BRS 323, Helio 358 and M734. The average grain yield of experiment was 2.043 kg.ha. For the NDF (number of days for physiological maturity) the genotypes performed differently and the M734, with 102 days, was the later, and the BRS 321, with 84 days, was the earlier