40 research outputs found
Magnetic circular dichroism as a local probe of the polarization ofa focused Gaussian beam
International audienc
Fizeau et lâentraĂnement partiel de lâĂ©ther
Entre 1849 et 1851, Hippolyte Fizeau a rĂ©alisĂ© successivement trois expĂ©riences fondamentales relatives Ă la vitesse de la lumiĂšre. Ce sont toutes trois de vĂ©ritables tours de force expĂ©rimentaux qui ont eu des consĂ©quences majeures dans lâĂ©volution de nos conceptions de la lumiĂšre et, comme lâa attestĂ© Albert Einstein lui-mĂȘme, dans lâavĂšnement de la relativitĂ© restreinte. Nous prĂ©sentons Ă la fois le contexte et les consĂ©quences historiques ainsi que la rĂ©plique moderne que nous avons rĂ©alisĂ©e de lâexpĂ©rience de 1851 dite « dâentraĂźnement partiel de lâĂ©ther »
Battements de photons uniques dans un interféromÚtre à base de modulateurs acousto-optiques
International audienceWe present in the following a quantum optics experiment appropriate for advanced undergraduate students with former experience in quantum optics. It extends classical single photon setups to the time dependent domain. We demonstrate self-heterodyning of heralded single photons using a Mach-Zender like interferometer where beamsplitters are replaced by two acousto-optic modulators (AOMs). The single pho-ton beat note is recorded over time at the frequency difference between the RF generators driving the AOMs, which makes it observable directly on a human time scale i. e. with periods above a fraction of a second. To compare with our observations, we tailor the standard quantum optics formalism for beam splitters to take into account the frequency shifts associated with the AOMs
Ab initio study of the enantio-selective magnetic-field-induced second harmonic generation in chiral molecules
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Unexpected optimal measurement protocols in Bell's inequality violation experiments
International audienceBell's inequality violation experiments are becoming increasingly popular in the practical teaching of undergraduate and master's degree students. Bell's parameter S is obtained from 16 polarization correlation measurements performed on entangled photons pairs. We first report here a detailed analysis of the uncertainty u( S) of Bell's parameter taking into account coincidence count statistics and errors in polarizers' orientation. We show using both computational modeling and experimental measurement that the actual sequence of the polarizer settings has an unexpected and strong influence on the error budget. This result may also be relevant to measurements in other settings in which errors in parameters may have non-random effects in the measurement
Expériences quantitatives et symétries du champ magnétique
National audienceLa plupart des smartphones sont Ă©quipĂ©s de capteurs Ă effet Hall 3D. Ils permettentde mettre facilement en Ă©vidence les symĂ©tries singuliĂšres du champ magnĂ©tique et rendentpossibles des positionnements prĂ©cis et des mesures que lâon peut comparer quantitativementĂ des modĂšles analytiques. Nous considĂ©rons tout dâabord lâexpĂ©rience historique dâĂrsted. Lesmesures sont trĂšs bien dĂ©crites par le modĂšle du fil infini. Nous Ă©tudions ensuite la spire carrĂ©edont le champ possĂšde une expression analytique dans tout lâespace. En fonction de la distanced du capteur au cĂŽtĂ© de la spire, on passe progressivement du modĂšle du fil infini Ă celui dudipĂŽle magnĂ©tique ce que lâon vĂ©rifie expĂ©rimentalement sur lâintensitĂ© du champ qui passe dâunedĂ©croissance en 1/d Ă 1/d^3