8,797 research outputs found
Theoretical investigation of moir\'e patterns in quantum images
Moir\'e patterns are produced when two periodic structures with different
spatial frequencies are superposed. The transmission of the resulting structure
gives rise to spatial beatings which are called moir\'e fringes. In classical
optics, the interest in moir\'e fringes comes from the fact that the spatial
beating given by the frequency difference gives information about details(high
spatial frequency) of a given spatial structure. We show that moir\'e fringes
can also arise in the spatial distribution of the coincidence count rate of
twin photons from the parametric down-conversion, when spatial structures with
different frequencies are placed in the path of each one of the twin beams. In
other words,we demonstrate how moir\'e fringes can arise from quantum images
Conservation of Orbital Angular Momentum in Stimulated Down-Conversion
We report on an experiment demonstrating the conservation of orbital angular
momentum in stimulated down-conversion. The orbital angular momentum is not
transferred to the individual beams of the spontaneous down-conversion, but it
is conserved when twin photons are taken individually. We observe the
conservation law for an individual beam of the down-conversion through
cavity-free stimulated emission.Comment: Submitted for publication in Phys. Rev. Let
Moir\'e patterns in quantum images
We observed moir\'e fringes in spatial quantum correlations between twin
photons generated by parametric down-conversion. Spatially periodic structures
were nonlocally superposed giving rise to beat frequencies typical of moir\'e
patterns. This result brings interesting perspectives regarding metrological
applications of such a quantum optical setup.Comment: 4 pages, 5 figure
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
Peletização de sementes de sorgo com calcário e com termofosfato e sua influência na absorção de fósforo e de potássio.
O trabalho foi realizado com o objetivo de avaliar a influencia da peletizacao de sementes de tres cultivares de sorgo (Sorghum bicolor (L.) Moench), cv. BRS 701, BRS 304 e BRS 601, com calcario e com termofosfato magnesiano, na absorcao de P e de K. Sementes peletizadas e nao peletizadas foram colocadas para germinar, por oito dias, em temperatura ambiente. Apos este periodo, oito plantulas com crescimento uniforme (parte aerea e raiz) foram distribuidas em vasos que continham solucao nutritiva completa de Hoagland. Apos 20 dias, iniciou-se a determinacao da absorcao de fosforo e de potassio por meio da deplecao desses nutrientes na solucao nutritiva. Os resultados permitiram concluir que o tipo de revestimento das sementes influenciou, de modo distinto, o crescimento de cada cultivar de sorgo. A absorcao de P e de K e o total absorvido tambem foram influenciados pelo revestimento das sementes em virtude do aumento no crescimento inicial das plantulas. De modo geral, independentemente do tipo de revestimento das sementes, houve maior absorcao de fosforo e de potassio quando as sementes foram peletizadas. A taxa de absorcao de fosforo aumentou com o peso da materia seca do sistema radicular e com o peso da materia seca da parte aerea, mas, neste caso, ate o limite de 3,5 umol planta-1 h-1 de P. Taxas de absorcao acima deste valor nao estiveram associadas ao aumento do peso da materia seca da parte aerea
Experimental investigation of dynamical invariants in bipartite entanglement
The non-conservation of entanglement, when two or more particles interact,
sets it apart from other dynamical quantities like energy and momentum. It does
not allow the interpretation of the subtle dynamics of entanglement as a flow
of this quantity between the constituents of the system. Here we show that
adding a third party to a two-particle system may lead to a conservation law
that relates the quantities characterizing the bipartite entanglement between
each of the parties and the other two. We provide an experimental demonstration
of this idea using entangled photons, and generalize it to N-partite GHZ
states
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