Etude théorique et expérimentale de mesures quantiques non-destructives de l'intensité d'un faisceau lumineux, réalisées à l'aide de non-linéarités à deux photons.

Abstract : The subject of this work is the study of Quantum Non-Demolition (QND) Measurements - in Optics. We show, both theoretically and experimentally, that such measurements can be performed using a non-linear coupling between two light beams. This interaction is obtained with a two-photon transition, inside a sodium atomic beam. The principle of this experiment is to use the crossed-phase modulation (crossed-Kerr effect), so as to transfer non-destructively the quantum intensity fluctuations of a laser beam, taken as the "signal", to the phase fluctuations of another beam, used as the "meter". The non-linear medium is located in a cavity. It is then possible to enhance the coupling between the two bearns, and also to use the cavity as an interferometric detector, which allows one to read out the phase fluctuations of the meter beam. The QND measurement can be characterized by simple parameters, which are directly measured. The experimental results that we obtained clearly show that our set-up has an actual efficiency above the quantum limit, appearing in standard coupling devices such as a beamsplitter. An analysis of a two-photon double-beam bistable device, in the dispersive and highfinesse limits, is also presented. The experimental results are compared with a simple crossedphase modulation model, and also with a numerical solution of the interaction between the cavity fields and three-level atoms, using the Optical Bloch Equations. Finally, we analyze several new quantum noise reduction effects, allowed by this system.
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Submitted on : Tuesday, July 3, 2012 - 4:45:13 PM
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Jean-François Roch. Etude théorique et expérimentale de mesures quantiques non-destructives de l'intensité d'un faisceau lumineux, réalisées à l'aide de non-linéarités à deux photons.. Optique [physics.optics]. Université Paris Sud - Paris XI, 1992. Français. ⟨pastel-00714237⟩

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