115 research outputs found
Health surveillance and geography: Theoretical and methodological potential
Objectives: To contribute to constructing recognition methodologies in the field by means of secondary data on objects and their forms, namely conditions of action and means of existence of human endeavor; to contribute to health surveillance through the incorporation of particular geographic characteristics; to relate concepts and categories of the territorialization process of health surveillance practices
Energy and momentum entanglement in parametric downconversion
We present a simple treatment for the phenomenon of parametric downconversion
considering the coherent scattering of one pump photon into a photon pair by a
nonlinear crystal. The energy and momentum entanglement of the quantum state of
the generated twin photons are seen as a consequence of the fundamental
indistinguishability of the time and the position in which the photon pair is
created inside the crystal. We also discuss some consequences of the system
entanglement.Comment: 6 pages, 2 figures. v3: Minor changes on the text. Some references
were include
Cancellation of atmospheric turbulence effects in entangled two-photon beams
Turbulent airflow in the atmosphere and the resulting random fluctuations in
its refractive index have long been known as a major cause of image
deterioration in astronomical imaging and figures among the obstacles for
reliable optical communication when information is encoded in the spatial
profile of a laser beam. Here we show that using correlation imaging and a
suitably prepared source of photon pairs, the most severe of the disturbances
inflicted on the beam by turbulence can be cancelled out. Other than a
two-photon light source, only linear passive optical elements are needed and,
as opposed to adaptive optics techniques, our scheme does not rely on active
wavefront correction.Comment: 5 pages, 3 figure
Experimental observation of spatial antibunching of photons
We report an interference experiment that shows transverse spatial
antibunching of photons. Using collinear parametric down-conversion in a
Young-type fourth-order interference setup we show interference patterns that
violate the classical Schwarz inequality and should not exist at all in a
classical description.Comment: 4 pages, 7 figure
Hong-Ou-Mandel interferometer with cavities: theory
We study the number of coincidences in a Hong-Ou-Mandel interferometer exit
whose arms have been supplemented with the addition of one or two optical
cavities. The fourth-order correlation function at the beam-splitter exit is
calculated. In the regime where the cavity length are larger than the
one-photon coherence length, photon coalescence and anti-coalescence
interference is observed. Feynman's path diagrams for the indistinguishable
processes that lead to quantum interference are presented. As application for
the Hong-Ou-Mandel interferometer with two cavities, it is discussed the
construction of an optical XOR gate
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