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Comportement quantique des appareils de mesure : illustrations en optique quantique

Abstract : This thesis explores the quantum behavior of measurement apparatus with illustrations in quantum optics. This is the first study of quantum properties of measurements performed by any kind of devices. We show that the quantum properties of a measurement, such as its projective or non-classical character, are revealed only by the quantum states of an unusual approach of quantum physics: the retrodictive approach. This approach involves retro-predictions about state preparations leading to a given measurement result, contrary to the predictive approach with which we usually make predictions about the results of an experiment. By clarifying the mathematical foundations of the retrodictive approach, we propose a general procedure for reconstructing the quantum states of this approach: the retrodicted states. We have realized these reconstructions for single-photon detectors, widely used in quantum cryptography for instance. This is the first tomography of quantum states totally based on the retrodictive approach and preparation choices, contrary to usual reconstructions based on measurement results. These tomographies enabled us to study experimentally the noise influence on the quantum properties of measurements performed by these detectors, in particular their transition from a strongly quantum behavior into a more classical behavior. Finally, we propose a detector of "Schrödinger's Cat" states of light, which are superpositions of incompatible quasi-classical states of light. In a modern version of a thought experiment proposed by Eugene Wigner in 1961, such a device could allow the "Wigner's Friend" to detect a "Schrödinger's Cat", contrary to human eyes for which we specify some quantum properties. We generalize the use of such a non-classical detector to an estimation protocol, totally based on the retrodictive approach and preparation choices. Such a procedure could enable optimal estimations, by reaching the quantum Cramér-Rao bound, which is a very topical issue of quantum metrology.
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https://tel.archives-ouvertes.fr/tel-00596762
Contributor : Taoufik Amri <>
Submitted on : Saturday, November 5, 2011 - 3:30:25 PM
Last modification on : Thursday, December 10, 2020 - 12:38:46 PM
Long-term archiving on: : Monday, February 6, 2012 - 2:20:36 AM

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  • HAL Id : tel-00596762, version 3

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Taoufik Amri. Comportement quantique des appareils de mesure : illustrations en optique quantique. Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 2011. Français. ⟨tel-00596762v3⟩

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