Préparation et stabilisation d'un champ non classique en cavité par rétroaction quantique

Abstract : Feedback loops are central to most classical control procedures. A controller compares the signal measured by a sensor with the target value or set-point. It then adjusts an actuator to stabilize the signal around the target value. Generalizing this scheme to the quantum world must overcome a fundamental difficulty: the sensor measurement causes a random back-action on the system. In this manuscript, we demonstrate the first continuously operated quantum feedback loop. The system to be controlled is a mode of the electromagnetic field trapped in a very high finesse microwave Fabry-Perot cavity. Circular Rydberg atoms achieve a quantum non-demolition measurement of the photon number in the mode by the succession of weak measurements. Knowing the outcome of these measurements, and knowing all the experimental imperfections of the system, a classical computer estimates in real-time the density matrix of the field. It then calculates the amplitude of small classical microwave fields injected into the cavity in order to stabilize the field around a target state. In this thesis, we have been able to prepare on demand and stabilize Fock states containing from 1 to 4 photons.
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Submitted on : Tuesday, December 20, 2011 - 6:01:26 PM
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  • HAL Id : tel-00654082, version 1

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Clément Sayrin. Préparation et stabilisation d'un champ non classique en cavité par rétroaction quantique. Physique Quantique [quant-ph]. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00654082⟩

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