Thèse soutenue

Puce à atomes supraconductrice : atomes à froids dans un environnement cryogénique et excitation d'atomes de Rydberg
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Auteur / Autrice : Andreas Emmert
Direction : Jean-Michel Raimond
Type : Thèse de doctorat
Discipline(s) : Physique quantique
Date : Soutenance en 2009
Etablissement(s) : Paris 6

Résumé

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Atom-chips are a versatile tool for the manipulation of cold atoms with magnetic potentials created by microstructures. However, one observes significant atom losses in those traps caused by spin-flip transitions, induced by radio-frequency fluctuations of the magnetic field, when the atoms are close to the chip surface. These fluctuations are due to Johnson-Nyquist noise in metallic structures. In our setup, the lifetime of atoms far away from the chip in a cryogenic environment is very long due to a low residual pressure obtained by cryogenic pumping. At a distance of several tens of micrometers yet, the lifetime is still limited by Johnson-Nyquist noise. One solution to this problem is the use of a purely superconducting environment, even in the realistic case of an atom-chip made of a type II superconductor containing vortices. We observe that the superconducting film influences the trapping potential, demonstrating the presence of micrometer size permanent supercurrents. We are able to induce these currents on demand with the potentiality to create complex traps. A cryogenic atom-chip can also be used for trapping strongly excited atoms (Rydberg atoms) which have a huge transition dipole moment that could be coupled to mesoscopic solid-state quantum systems. This long-term goal in mind, we have adapted our experiment for the excitation of Rydberg atoms. First excitation spectra reveal a parasitic electric field in the close vicinity of the atom-chip which is sufficiently weak for the next step of our experiment, the excitation of an single atom on demand using the dipole blockade effect.