Quantum computing with incoherent resources and quantum jumps

Spontaneous emission and the inelastic scattering of photons are two natural processes usually associated with decoherence and the reduction in the capacity to process quantum information. Here we show that when suitably detected, these photons are sufficient to build all the fundamental blocks needed to perform quantum computation in the emitting qubits while protecting them from deleterious dissipative effects. We exemplify by showing how to teleport an unknown quantum state and how to efficiently prepare graph states for the implementation of measurement-based quantum computation.Comment: 5 pages, 5 figure

The Geometry of Entanglement Sudden Death

In open quantum systems, entanglement can vanish faster than coherence. This phenomenon is usually called sudden death of entanglement. In this paper sudden death of entanglement is discussed from a geometrical point of view, in the context of two qubits. A classification of possible scenarios is presented, with important known examples classified. Theoretical and experimental construction of other examples is suggested as well as large dimensional and multipartite versions of the effect.Comment: 6 pages, 2 figures, references added, initial paragraph corrected, sectioning adopted, some parts rewritten; accepted by New J. Phy

Asymptotic Entanglement Dynamics and Geometry of Quantum States

A given dynamics for a composite quantum system can exhibit several distinct properties for the asymptotic entanglement behavior, like entanglement sudden death, asymptotic death of entanglement, sudden birth of entanglement, etc. A classification of the possible situations was given in [M. O. Terra Cunha, {\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no known examples. In this work we give a better classification for the possibile relaxing dynamics at the light of the geometry of their set of asymptotic states and give explicit examples for all the classes. Although the classification is completely general, in the search of examples it is sufficient to use two qubits with dynamics given by differential equations in Lindblad form (some of them non-autonomous). We also investigate, in each case, the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J. Phys. A: Math. Theo

Soil classification from visible/near-infrared diffuse reflectance spectra at multiple depths.

Abstract : Visible/near-infrared diffuse reflectance spectroscopy (VNIRS) offers an alternative to conventional analytical methods to estimate various soil attributes. However, the use of VNIRS in soil survey and taxonomic classification is still underexplored. We investigated the potential use of VNIRS to classify soils in a region with variable soils, geology, and topography in southeastern Brazil. We combined principal component (PC) analysis, and multinomial logistic regression to classify 291 soils at the levels of suborder (second highest), and suborder with textural classification (STC), described in the field according to the Brazilian Soil Classification System. Soil visible/near-infrared (400-2500 nm) spectra were collected from three depth intervals (0-20, 40-60, and 80-100 cm), and combined in sequence to compose a pseudo multi-depth spectral curve, which was used to derive the classification models. The percent of correctly classified soils at the suborder level was 79% using 20 PCs, and 96% using 30 PCs. At the STC level, soils were correctly classified in 100%, and 78% of the cases using 20, and 30 PCs, respectively. Given the inherent complexity and variability within soil taxonomic groups, and in contrast the similarity among different groups, combining spectral data from different depths in multivariate classification offered a simple and inexpensive solution to adequately distinguish soils. This novel approach could improve soil classification and survey in a cost-efficient manner, supporting sustainable use, and management of tropical soils

The algal flora of the Azores: a historical and biogeographical approach.

43rd European Marine Biology Symposium. Ponta Delgada, Açores, 8-12 de Setembro de 2008

Detection of ochratoxin A in tropical wine and grape juice from Brazil.

Ochratoxin A (OTA) is the main mycotoxin found in grapes, wines and grape juices and is considered one of the most harmful contaminants to human health. In this study, samples of tropical wines and grape juices from different grape varieties grown in Brazil were analysed for their OTA content by high-performance liquid chromatography. The detection and quantification limits for OTA were 0.01 and 0.03 &#956;g L&#8722;1 respectively. OTA was detected in 13 (38.24%) of the samples analysed, with concentrations ranging from <0.03 to 0.62 &#956;g L&#8722;1. OTA was not detected in any of the grape juice samples. Most of the red wine samples proved to be contaminated with OTA (75%), while only one white wine sample was contaminated. However, the OTA levels detected in all samples were well below the maximum tolerable limit (2 &#956;g L&#8722;1) in wine and grape juice established by the European Community and Brazilian legislature. The results of this study indicate a low risk of exposure to OTA by consumption of tropical wines and grape juices from Brazil

Aspergillus ocratoxigênicos em uvas e no solo de cultivo da variedade Sauvignon Blanc no Nordeste brasileiro.

A ocratoxina A (OTA) é um metabólito secundário de fungos freqüentemente encontrado como contaminante de uvas, vinhos e suco de uva, sendo considerada uma das micotoxinas mais prejudiciais para a saúde humana. Este estudo teve como objetivo avaliar a incidência de Aspergillusocratoxigênicos em uvas e no solo de cultivo da variedade Sauvignon Blanc utilizada para produção de vinho no nordeste brasileiro. As amostras de uva e de solo foram coletadas em uma região vitivinícola do Submédio São Francisco (Casa Nova, Bahia). Para o isolamento de fungos das uvas e sementes utilizou-se a Técnica de Plaqueamento Direto em meio de cultura DRBC (Dicloran Rosa Bengal Cloranfenicol); para a amostra de solo foi utilizada a técnica de espalhamento superficial, em DG 18 (Dichloran 18% Glycerol Agar), a partir de diluições seriadas. Selecionou-se para obtenção de culturas puras apenas os fungos do gênero Aspergillus que foram identificados por características morfológicas e avaliados, quanto à produção de OTA, pelo Método Plug Agar. Das uvas foram isoladas e identificadas as seguintes espécies A. foetidus, A. tubingensis e A. sp.. Destes isolados nenhum foi ocratoxigênico. Dos vinte e nove isolados obtidos do solo, quatro foram ocratoxigênicos (A. niger agregado (1), A. carbonarius agregado (2) e A. carbonarius (1)), o que realça a importância de evitar durante a colheita o contato das uvas com o solo, visto que este pode representar uma fonte de contaminação com esta micotoxina para as uvas e vinhos. Palavras-chaves: Fungos ocratoxigênicos, Uvas, Aspergillus, Ocratoxina A, Solo, Sauvignon Blan

Azorean Coastal Communities. An On-going Study.

43rd European Marine Biology Symposium. Ponta Delgada, Açores, 8-12 de Setembro de 2008

Absolute and convective instabilities of parallel propagating circularly polarized Alfvén waves: numerical results

Context.The stability of parallel propagating circularly polarized Alfvén waves (pump waves) has been studied for more than four decades with the use of normal mode analysis. It is well known that the normal mode analysis does not answer the question if a pump wave looks stable or unstable in a particular reference frame. To answer this question it is necessary to find out if the instability is absolute or convective in this reference frame. Aims.We extend our previous study of absolute and convective instabilities of pump waves with small amplitude to pump waves with arbitrary amplitude. Methods.To study the absolute and convective instabilities of pump waves with arbitrary amplitude we numerically implement Brigg's method. Results.We show that the wave is absolutely unstable in a reference frame moving with the velocity U with respect to the rest plasma if U satisfies the inequality Ul Ur) we study the signalling problem. We show that spatially amplifying waves exist only when the signalling frequency is in two symmetric frequency bands, and calculate the dependences of the boundaries of these bands on U for different values of a . We also obtain the dependences of the maximum spatial amplification rate on U for different values of a . The implication of these results on the interpretation of observational data from space missions is discussed. In particular, it is shown that circularly polarized Alfvén waves propagating in the solar wind are convectively unstable in a reference frame of any realistic spacecraft