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Abstract : We present here the realisation of a conditional quantum dynamics and the preparation of an entangled state of three quantum systems in a cavity quantum electrodynamics experiment. We couple atoms, prepared in a circular Rydberg state, to the mode of a very high $Q$ cavity, prepared in the vacuum state. At resonance, a reversible and coherent exchange of one quantum of excitation takes place : The quantum Rabi oscillation. By fixing the interaction time to a complete cycle of absorption and emission, we obtain a conditional dynamics : The quantum phase of the atom--field state changes if the mode contains a photon and if the atomic state is coupled to the mode. On the other hand, if the mode does not contain a photon or the atomic state is not coupled, the phase stays unchanged. We demonstrate this phase shift and we vary its value by detuning the mode frequency with respect to the atomic transition. Furthermore, we verify that the dynamics preserves the coherence of the sub-systems and hence results in an entangled state if they are initially prepared in state superpositions. We interpret the process in terms of a quantum logic gate and we analyse its limitations. In a second experiment, we prepare and analyse an entangled state between two atoms and the field, using successive and reversible operations. The first atom gets entangled with the field while interacting with it during a quarter of a Rabi oscillation. The second atom then undergoes, like in the first experiment, a complete Rabi oscillation. Being prepared in a superposition of the coupled and the uncoupled state, it equally becomes entangled with the field, and thus also with the first atom. Measurements in two orthogonal bases are carried out on the resulting three-system entangled state. An analysis of the experimental signals is presented. It confirms that the prepared state is in fact not separable. We discuss the perspectives opened by these experiments for quantum information processing.
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Contributor : Arno Rauschenbeutel <>
Submitted on : Tuesday, October 16, 2001 - 12:00:00 AM
Last modification on : Thursday, December 10, 2020 - 12:36:56 PM
Long-term archiving on: : Friday, April 2, 2010 - 7:49:23 PM


  • HAL Id : tel-00000826, version 1


Arno Rauschenbeutel. ATOMES ET CAVITÉ : PRÉPARATION ET MANIPULATION D'ÉTATS INTRIQUÉS COMPLEXES. Physique Atomique [physics.atom-ph]. Université Pierre et Marie Curie - Paris VI, 2001. Français. ⟨tel-00000826⟩



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