A higher quantum bound for the V\'ertesi-Bene-Bell-inequality and the role of POVMs regarding its threshold detection efficiency

Recently, V\'{e}rtesi and Bene [Phys. Rev. A. {\bf 82}, 062115 (2010)] derived a two-qubit Bell inequality, $I_{CH3}$, which they show to be maximally violated only when more general positive operator valued measures (POVMs) are used instead of the usual von Neumann measurements. Here we consider a general parametrization for the three-element-POVM involved in the Bell test and obtain a higher quantum bound for the $I_{CH3}$-inequality. With a higher quantum bound for $I_{CH3}$, we investigate if there is an experimental setup that can be used for observing that POVMs give higher violations in Bell tests based on this inequality. We analyze the maximum errors supported by the inequality to identify a source of entangled photons that can be used for the test. Then, we study if POVMs are also relevant in the more realistic case that partially entangled states are used in the experiment. Finally, we investigate which are the required efficiencies of the $I_{CH3}$-inequality, and the type of measurements involved, for closing the detection loophole. We obtain that POVMs allow for the lowest threshold detection efficiency, and that it is comparable to the minimal (in the case of two-qubits) required detection efficiency of the Clauser-Horne-Bell-inequality.Comment: 11 Pages, 16 Figure

Interference and complementarity for two-photon hybrid entangled states

In this work we generate two-photon hybrid entangled states (HES), where the polarization of one photon is entangled with the transverse spatial degree of freedom of the second photon. The photon pair is created by parametric down-conversion in a polarization-entangled state. A birefringent double-slit couples the polarization and spatial degrees of freedom of these photons and finally, suitable spatial and polarization projections generate the HES. We investigate some interesting aspects of the two-photon hybrid interference, and present this study in the context of the complementarity relation that exists between the visibilities of the one- and two-photon interference patterns.Comment: 10 pages, 4 figures. Accepted in Physical Review

Gauging the SU(2) Skyrme model

In this paper the SU(2) Skyrme model will be reformulated as a gauge theory and the hidden symmetry will be investigated and explored in the energy spectrum computation. To this end we purpose a new constraint conversion scheme, based on the symplectic framework with the introduction of Wess-Zumino (WZ) terms in an unambiguous way. It is a positive feature not present on the BFFT constraint conversion. The Dirac's procedure for the first-class constraints is employed to quantize this gauge invariant nonlinear system and the energy spectrum is computed. The finding out shows the power of the symplectic gauge-invariant formalism when compared with another constraint conversion procedures present on the literature.Comment: revised version, to appear in Phys.Rev.

Desempenho Produtivo de Genótipos de Arroz Irrigado sob Estresse Salino na Fase Reprodutiva.

RESUMO- A salinização da água dos mananciais que irrigam as lavouras de arroz da Planície Costeira do Rio Grande do Sul tem causado perdas em produtividade à cultura. A intensidade com que o estresse salino influencia o desempenho da cultura varia com o genótipo e estádio fenológico. Realizou-se um trabalho para avaliar avaliar o efeito do nível de sal na água de irrigação, aplicada durante a fase reprodutiva, no desempenho produtivo de genótipos de arroz. O experimento foi realizado em tanques de alvenaria dispostos ao ar livre, nos quais cultivaram-se doze genótipos de arroz irrigado, seis de ciclo precoce (BRS Querência, BRS Pampa, BRA050106, AB06046, AB09025 e AB10101) e seis de ciclo médio (BRS Bojuru, BRS Sinuelo CL, BRS Cirad 302, AB08020, BRA040291 e CNAi9903). A irrigação do arroz iniciou no estádio quatro folhas, mas a aplicação dos tratamentos de sal (água natural e soluções 0,25% e 0,50% de NaCl) ocorreu, apenas, no início da fase reprodutiva, estendendo-se até a maturação, quando se procedeu a avaliação do desempenho produtivo dos genótipos de arroz. O excesso de sal na água de irrigação na fase reprodutiva reduziu o número de perfilhos, a produção e massa de grãos e aumentou a esterilidade de espiguetas do arroz. O efeito depressivo do sal foi mais intenso para os genótipos de ciclo precoce, relativamente àqueles de ciclo médio. A salinidade da água de irrigação afeta o desempenho produtivo de genótipos de arroz; a magnitude desse efeito é proporcional ao nível de sal na água, variando em intensidade entre genótipos

Desempenho Produtivo de Genótipos de Arroz Irrigado sob Estresse Salino na Fase Reprodutiva.

RESUMO- A salinização da água dos mananciais que irrigam as lavouras de arroz da Planície Costeira do Rio Grande do Sul tem causado perdas em produtividade à cultura. A intensidade com que o estresse salino influencia o desempenho da cultura varia com o genótipo e estádio fenológico. Realizou-se um trabalho para avaliar avaliar o efeito do nível de sal na água de irrigação, aplicada durante a fase reprodutiva, no desempenho produtivo de genótipos de arroz. O experimento foi realizado em tanques de alvenaria dispostos ao ar livre, nos quais cultivaram-se doze genótipos de arroz irrigado, seis de ciclo precoce (BRS Querência, BRS Pampa, BRA050106, AB06046, AB09025 e AB10101) e seis de ciclo médio (BRS Bojuru, BRS Sinuelo CL, BRS Cirad 302, AB08020, BRA040291 e CNAi9903). A irrigação do arroz iniciou no estádio quatro folhas, mas a aplicação dos tratamentos de sal (água natural e soluções 0,25% e 0,50% de NaCl) ocorreu, apenas, no início da fase reprodutiva, estendendo-se até a maturação, quando se procedeu a avaliação do desempenho produtivo dos genótipos de arroz. O excesso de sal na água de irrigação na fase reprodutiva reduziu o número de perfilhos, a produção e massa de grãos e aumentou a esterilidade de espiguetas do arroz. O efeito depressivo do sal foi mais intenso para os genótipos de ciclo precoce, relativamente àqueles de ciclo médio. A salinidade da água de irrigação afeta o desempenho produtivo de genótipos de arroz; a magnitude desse efeito é proporcional ao nível de sal na água, variando em intensidade entre genótipos

Metastability and Nucleation for the Blume-Capel Model. Different mechanisms of transition

We study metastability and nucleation for the Blume-Capel model: a ferromagnetic nearest neighbour two-dimensional lattice system with spin variables taking values in -1,0,+1. We consider large but finite volume, small fixed magnetic field h and chemical potential "lambda" in the limit of zero temperature; we analyze the first excursion from the metastable -1 configuration to the stable +1 configuration. We compute the asymptotic behaviour of the transition time and describe the typical tube of trajectories during the transition. We show that, unexpectedly, the mechanism of transition changes abruptly when the line h=2*lambda is crossed.Comment: 96 pages, 44 tex-figures, 7 postscript figure

The SNF2-Family Member Fun30 Promotes Gene Silencing in Heterochromatic Loci

Chromatin regulates many key processes in the nucleus by controlling access to the underlying DNA. SNF2-like factors are ATP-driven enzymes that play key roles in the dynamics of chromatin by remodelling nucleosomes and other nucleoprotein complexes. Even simple eukaryotes such as yeast contain members of several subfamilies of SNF2-like factors. The FUN30/ETL1 subfamily of SNF2 remodellers is conserved from yeasts to humans, but is poorly characterized. We show that the deletion of FUN30 leads to sensitivity to the topoisomerase I poison camptothecin and to severe cell cycle progression defects when the Orc5 subunit is mutated. We demonstrate a role of FUN30 in promoting silencing in the heterochromatin-like mating type locus HMR, telomeres and the rDNA repeats. Chromatin immunoprecipitation experiments demonstrate that Fun30 binds at the boundary element of the silent HMR and within the silent HMR. Mapping of nucleosomes in vivo using micrococcal nuclease demonstrates that deletion of FUN30 leads to changes of the chromatin structure at the boundary element. A point mutation in the ATP-binding site abrogates the silencing function of Fun30 as well as its toxicity upon overexpression, indicating that the ATPase activity is essential for these roles of Fun30. We identify by amino acid sequence analysis a putative CUE motif as a feature of FUN30/ETL1 factors and show that this motif assists Fun30 activity. Our work suggests that Fun30 is directly involved in silencing by regulating the chromatin structure within or around silent loci

Experimental quantum tomography of photonic qudits via mutually unbiased basis

We present the experimental quantum tomography of 7- and 8-dimensional quantum systems based on projective measurements in the mutually unbiased basis (MUB-QT). One of the advantages of MUB-QT is that it requires projections from a minimal number of bases to be performed. In our scheme, the higher dimensional quantum systems are encoded using the propagation modes of single photons, and we take advantage of the capabilities of amplitude- and phase-modulation of programmable spatial light modulators to implement the MUB-QT.Comment: Published versio

Symmetry Breaking and Finite Size Effects in Quantum Many-Body Systems

We consider a quantum many-body system on a lattice with a continuous symmetry which exhibits a spontaneous symmetry breaking in its infinite volume ground states, but in which the order operator does not commute with the Hamiltonian. A typical example is the Heisenberg antiferromagnet with a Neel order. In the corresponding finite system, the symmetry breaking is usually "obscured" by "quantum fluctuation" and one gets a symmetric ground state with a long range order. In such a situation, we prove that there exist ever increasing numbers of low-lying eigenstates whose excitation energies are bounded by a constant times 1/N, where N denotes the number of sites. By forming linear combinations of these low-lying states and the (finite-volume) ground state, and by taking infinite volume limits, we construct infinite volume ground states with explicit symmetry breaking. Our general theorems do not only shed light on the nature ofsymmetry breaking in quantum many-body systems, but provide indispensable information for numerical approaches to these systems. We also discuss applications of our general results to a variety of examples. The present paper is intended to be accessible to the readers without background in mathematical approaches to quantum many-body systems.Comment: LaTeX, 58 pages, no figures. Notes about Bose-Einstein condenstaion are added after the publicatio