1,823 research outputs found
High efficiency coupling of photon pairs in practice
Multi-photon and quantum communication experiments such as loophole-free Bell
tests and device independent quantum key distribution require entangled photon
sources which display high coupling efficiency. In this paper we put forward a
simple quantum theoretical model which allows the experimenter to design a
source with high pair coupling efficiency. In particular we apply this approach
to a situation where high coupling has not been previously obtained: we
demonstrate a symmetric coupling efficiency of more than 80% in a highly
frequency non-degenerate configuration. Furthermore, we demonstrate this
technique in a broad range of configurations, i.e. in continuous wave and
pulsed pump regimes, and for different nonlinear crystals
Pulsed source of spectrally uncorrelated and indistinguishable photons at telecom wavelengths
We report on the generation of indistinguishable photon pairs at telecom
wavelengths based on a type-II parametric down conversion process in a
periodically poled potassium titanyl phosphate (PPKTP) crystal. The phase
matching, pump laser characteristics and coupling geometry are optimised to
obtain spectrally uncorrelated photons with high coupling efficiencies. Four
photons are generated by a counter- propagating pump in the same crystal and
anlysed via two photon interference experiments between photons from each pair
source as well as joint spectral and g^(2) measurements. We obtain a spectral
purity of 0.91 and coupling efficiencies around 90% for all four photons
without any filtering. These pure indistinguishable photon sources at telecom
wavelengths are perfectly adapted for quantum network demonstrations and other
multi-photon protocols
Ulcerative colitis: let's talk about extent
Ulcerative colitis (UC) is a chronic inflammatory disease in which clinical course varies substantially between patients.
The extent of the disease is usually pointed out as one of the factors
responsible for this variation. With this study, we pretended to evaluate the differences in natural history and pharmacological therapy
prescription between left-sided and extended UC
Análise de associação genômica ampla baseada em conjunto de genes: implementação em R.
O objetivo deste trabalho é a criação de um pacote R (R CORE TEAM, 2014) que implemente quatro diferentes métodos de GSEA no contexto de GWAS, considerando adaptações para aplicação em espécies animais de interesse para a agricultura
Tuned liquid dampers simulation for earthquake response control of buildings
This paper is focused on the study of an earthquake protection system, the Tuned Liquid Damper (TLD), which
can, if adequately designed, reduce earthquake demands on buildings. This positive effect is accomplished taking
into account the oscillation of the free surface of a fluid inside a tank (sloshing). The behaviour of an isolated
Tuned Liquid Damper, subjected to a sinusoidal excitation at its base, with different displacement amplitudes,
was studied by finite element analysis. The efficiency of the TLD in improving the seismic response of an existing building, representative of modern architecture buildings in southern European countries was also evaluated based on linear dynamic analyses
Nonlinear interaction between two heralded single photons
Harnessing nonlinearities strong enough to allow two single photons to
interact with one another is not only a fascinating challenge but is central to
numerous advanced applications in quantum information science. Currently, all
known approaches are extremely challenging although a few have led to
experimental realisations with attenuated classical laser light. This has
included cross-phase modulation with weak classical light in atomic ensembles
and optical fibres, converting incident laser light into a non-classical stream
of photon or Rydberg blockades as well as all-optical switches with attenuated
classical light in various atomic systems. Here we report the observation of a
nonlinear parametric interaction between two true single photons. Single
photons are initially generated by heralding one photon from each of two
independent spontaneous parametric downconversion sources. The two heralded
single photons are subsequently combined in a nonlinear waveguide where they
are converted into a single photon with a higher energy. Our approach
highlights the potential for quantum nonlinear optics with integrated devices,
and as the photons are at telecom wavelengths, it is well adapted to
applications in quantum communication.Comment: 4 pages, 4 figure
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