Heidelberg 1999 – wissenschaftliches Programm
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Q: Quantenoptik
Q 40: Poster: Fallen und Kühlung
Q 40.3: Poster
Donnerstag, 18. März 1999, 16:30–18:30, PH
Laser cooling of two trapped ions beyond the Lamb-Dicke regime — •Giovanna Morigi1, Jürgen Eschner2, Ignacio Cirac1, and Peter Zoller1 — 1Institut für Theoretische Physik, U Innsbruck, Technikerstr. 25, A-6020 Innsbruck — 2Institut für Experimentalphysik, U Innsbruck, Technikerstr. 25, A-6020 Innsbruck
We study laser cooling of two ions that are trapped in a harmonic potential and interact by Coulomb repulsion. Sideband cooling in the Lamb-Dicke regime is shown to work analogously to sideband cooling of a single ion. Outside the Lamb-Dicke regime, the incommensurable frequencies of the two vibrational modes result in a quasi-continuous energy spectrum that significantly alters the cooling dynamics. The cooling time decreases nonlinearly with the linewidth of the cooling transition, and the effect of trapping states which may slow down the cooling is considerably reduced. We show that cooling to the ground state is possible also outside the Lamb-Dicke regime. We also show that a rate equation treatment is a good approximation in all cases. We then study Doppler cooling and show that it may work as an efficient precooling technique, thus optimizing the final sideband cooling phase. Finally we propose and discuss a model for Doppler cooling of a string of N ions outside the Lamb-Dicke regime.