Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environment

We report on an experimental investigation of the dynamics of entanglement between a single qubit and its environment, as well as for pairs of qubits interacting independently with individual environments, using photons obtained from parametric down-conversion. The qubits are encoded in the polarizations of single photons, while the interaction with the environment is implemented by coupling the polarization of each photon with its momentum. A convenient Sagnac interferometer allows for the implementation of several decoherence channels and for the continuous monitoring of the environment. For an initially-entangled photon pair, one observes the vanishing of entanglement before coherence disappears. For a single qubit interacting with an environment, the dynamics of complementarity relations connecting single-qubit properties and its entanglement with the environment is experimentally determined. The evolution of a single qubit under continuous monitoring of the environment is investigated, demonstrating that a qubit may decay even when the environment is found in the unexcited state. This implies that entanglement can be increased by local continuous monitoring, which is equivalent to entanglement distillation. We also present a detailed analysis of the transfer of entanglement from the two-qubit system to the two corresponding environments, between which entanglement may suddenly appear, and show instances for which no entanglement is created between dephasing environments, nor between each of them and the corresponding qubit: the initial two-qubit entanglement gets transformed into legitimate multiqubit entanglement of the Greenberger-Horne-Zeilinger (GHZ) type.Comment: 15 pages, 14 figures; only .ps was working, now .pdf is also availabl

Emergence of the pointer basis through the dynamics of correlations

We use the classical correlation between a quantum system being measured and its measurement apparatus to analyze the amount of information being retrieved in a quantum measurement process. Accounting for decoherence of the apparatus, we show that these correlations may have a sudden transition from a decay regime to a constant level. This transition characterizes a non-asymptotic emergence of the pointer basis, while the system-apparatus can still be quantum correlated. We provide a formalization of the concept of emergence of a pointer basis in an apparatus subject to decoherence. This contrast of the pointer basis emergence to the quantum to classical transition is demonstrated in an experiment with polarization entangled photon pairs.Comment: 4+2 pgs, 3 figures. Title changed. Revised version to appear on PR

Uso de funções discriminantes para comparação de cultivares dos gêneros Cynodon e Digitaria quanto à produção de matéria seca e teores de macronutrientes.

Foi realizado um experirnento no Centro Nacional de Pesquisa de Agrobiologia, Seropédica-RJ, com objetivo de comparar as gramineas Coast cross e Tifton 85, do gênero Cynodon, e as gramíneas Suazi (Digitaria swazilandensis) e Transvala (D. decumbens), do gênero Digitaria, quanto a produção de matéria seca (MS) e teores de macronutrientes da parte aérea e sistema radicular, em 15 amostras de cada cultivar, coletadas no período das chuvas (primavera/verão). A análise discriminante demonstrou que as variáveis Mg, Ca e MS na parte aérea e P e N na raiz foram importantes no processo de discriminação dos cultivares estudados. O cultivar Suázi foi diferente dos dernais avaliados quanto a produção de MS e aos teores de Mg e Ca na parte aérea, além do P e N na raiz. Os cultivares Tifton 85 e Coast cross, apesar de serem do mesmo gênero, diferem quanto a produção de MS e aos teores de Mg e Ca na parte aérea, alem do P e N na raiz. Algumas amostras dos cultivares Tifton 85 e Coast cross apresentaram semelhança com O capim Transvala, com relação a produção de MS e aos teores de Mg e Ca na parte aérea, alem de P e N na raiz. An experiment was carried out at the National Center of Research of Agrobiology, Seropedica--RJ, with objective of evaluating the grasses Coast cross (Cynodon spp.) and Tifton 85 (Cynodon dactylon (L.)), of the Cynodon genus, and the grasses Suazi (Digitaria swazilandensis) and Transvala (Digitaria decumbens), of the Digitaria genus, through the discriminant analysis. The evaluated variables were: dry matter production (DMP) and contents of nitrogen (N), phosphorus (P), magnesium (Mg) and calcium (Ca) in the shoot and root on 15 samples of each grasses, accomplished in the period of the rains (spring/ summer). The discriminant analysis demonstrated that the variables Mg, Ca and dry matter production (DMP) in shoot, and P and N root are important in the discrimination process of the Coast cross, Tifton 85, Suazi and Transvala cultivars. Suazi cultivar is clearly different from the others cultivars, in relationship to Mg and Ca contents and DMP at the shoot, P and N at the root. O Tifton 85 and Coast cross cultivars, in spite of being of the same genus, differ in relationship to Mg and Ca contents and DMP at the shoot, match and N at the root. Some samples of the Tifton 85 and Coast cross cultivars can be similar to the grass Transvala, in relation to the Mg, Ca and DMP contents in shoot, P and N root.Parceria: UFV; PESAGRO-Rio/ESS; UFRRJ; ESALQ

Estabelecimento de leguminosas arbóreas em pastos de capim-marandu e tanzânia.

Parceria: PESAGRO; UFRRJ

Efeitos de sombreamento em acessos de amendoim forrageiro (Arachis spp.) recomendados para o estado do Rio de Janeiro.

A literatura nao mostra resultados em relac;ao a influencia de sombreamento sobre os novos acessos e cultivares de amendoim forrage"rro. 0 objeffvo deste estudofoi avatfar a fnftuencfa de quatro nfveis artificiais de sombreamento (0, 25, 50 e 75%) e dois intervalos de cortes (45 e 90 dias), em sete variiweis (produc;ao de materia seca foliar, caulinar, radicular e parte aerea; relac;ao folha/caule; area foliar e area fotiar especffica) de tres acessos de amendoim forrageiro (BRA 031496 de Arachis pintoi e BRA 031861 e BRA 031801 de Arachis repens), recomendados para 0 estado do Rio de Janeiro. 0 delineamento experimental adotado foi 0 blocos ao acaso, dispostos em parcefas subdfvididas com tres repetic;6es. as niveis de sombreamento representando as parcelas, e 0 fatorial tres acessos com dois intervalos de corte, representando as sub-parcelas. Na analise estatfstica dos resultados, realizada por meio de analise de fatores ou analise fa to ria', utffizou-se 0 programa SAEG versao 9.0. Observou-se a existencia de correlac;ao entre as variaveis, exceto para a produc;ao de materia seca de rafzes. 0 primeiro fator rotacionado (F1), responsavel pela explicac;ao da maior porcentagem da variancia observada (67,7%), mostrou que 0 nlvel de sombreamento mais dense (75%), proporcionou as maiores produc;6es de materia seca foliar, caulinar, da parte aerea e area foliar de plantas dos acessos BR 031496 e BR 031801 de amendoim forrageiro, quando cortados com intervalos de 90 dias. Os resultados indicam que os acessos de amendoim forrageiro BR 031496 e BR 031801, recomendados para a regiao, toleram nfveis de sombreamento mais densos nos sistemas silvipastoris ou como cobertura de solo, sob culturas comerciais, desde que manejados com perfodo maior de pousio. Published results do not show results regarding the influence of shading on accessions and cultivars new of forage peanut. This study aimed the evaluation of the influence of four shading levels (0, 25, 50 and 75%) and two cutting intervals (45 and 90 days) on seven plant variables (dry matter production of leaves, stem, roots and whole shoots; leaf/stem ratio; leaf area and specific leaf area) of three forage peanut accessions (BRA 031496 of Arachis pintoi and BRA 031861 and BRA 031801 of Arachis repens) recommended for the Baixada Fluminense region. The experimental design adopted was in split-plot randomised blocks with three replicates. The shading levels represented the main plots and the factorial accessions x cutting intervals, the subplots. The software SAEG 9.0 version was used for statistical analysis. Correlation among variables were observed exception made to root dry matter production. The first rotated factor (F1), which explains most of the observed variance (67.7%), indicated that the highest shading (75%) brought about the greatest dry matter production of leaves) stems and whole shoot and highest leaf area of the BR 031496 and BR 031801 accessions of forage peanut when cut at 90 days intervals. According to the results the BR 031496 and BR 031801 accessions of forage peanut, recommended for the region, tDJerQte high Jev-eJs of shading. in either sHvjpasmral systems or as green-mulch for commercial crops, always larger cutting intervals are adopted.bitstream/CNPAB-2010/34842/1/bot023.pdfParceria: UFRRJ; PESAGRO

Influência da adubação nitrogenada na forma de chorume bovino na matéria seca e nutrientes acumulados nas raízes de gramíneas forrageiras.

bitstream/CNPAB-2010/32085/1/bot005.pd