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Étude du couplage de petits systèmes quantiques avec leur environnement: fluctuations et décohérence à basse température

Abstract : In this thesis, we discuss the influence of a zero temperature environment on a small quantum system in the framework of a very simple model: a harmonic oscillator ("the particle") coupled to a bath of harmonic oscillators ("the environment"). First, we study the equilibrium state of the total system, using the "reduced resolvent" approach, well-known in spectral theory. We calculate the reduced density operator of the particle. At low temperature, the environment induces effective thermal effects. Then, by using the same method, we consider the time-evolution of the reduced density operator of the particle. The latter converges to the equilibrium state, despite the unitary evolution of the total system. These results can be transposed to quantum electric circuits. With the same formalism we consider the coupling between a mechanical system (a harmonic oscillator) and an electric environment (an ohmic resistor). Finally, we propose an experimental device showing the effects induced by a controlled electric environment on a charged particle. We show that the particle's coherence length is reduced by the coupling between the particle and the environment. The effect persists in the zero temperature limit.
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https://tel.archives-ouvertes.fr/tel-00010840
Contributor : Alexandre Ratchov <>
Submitted on : Monday, October 31, 2005 - 2:05:41 PM
Last modification on : Thursday, November 19, 2020 - 3:52:33 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:54:15 PM

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  • HAL Id : tel-00010840, version 1

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Alexandre Ratchov. Étude du couplage de petits systèmes quantiques avec leur environnement: fluctuations et décohérence à basse température. Matière Condensée [cond-mat]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00010840⟩

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