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Chinese Physics Letters

A Single Laser Cooled Trapped ^40Ca^＋ Ion in a Miniature Paul Trap

舒华林

Published Jan 1, 2005• 1 citation
OpenAlex

Abstract

We have observed the phenomenon of phase transition of a few trapped ions in a miniature Paul trap. Judging from the quantum jump signa/s, a single laser-cooled trapped Ca^+ ion has been realized. The ion temperature is estimated to be 22 mK. The result shows that the amplitude of ion micromotion is strongly dependent on the rf voltage.

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A laser-cooling experiment with Ca+{\mathrm{Ca}}^{+}Ca+ ions trapped in a linear rf octupole ion trap is presented. The phase transition of the laser-cooled Ca+{\mathrm{Ca}}^{+}Ca+ ions from the cloud to the crystal state is observed by an abrupt dip of the laser-induced fluorescence spectrum and indicates that mK temperatures are obtained. We have also performed molecular dynamics simulations under various conditions to confirm this property by deducing axially symmetric structures of Coulomb crystals and by evaluating the translational temperatures of the laser-cooled ions. The simulation results show that for small numbers of ions novel ring-shaped crystals are produced. As the number of ions is increased, cylindrical layers in the ring crystal are sequentially formed. For more than 100 ions, also hexagonal and spiral structures emerge in parts of the large-size ion crystal, which has a length on the order of millimeters for the present geometrical arrangement and voltages. An advantage of the linear rf octupole trap is its large almost-field-free region in the middle of the trap, where the micromotion amplitude is small for trapped ions. These results demonstrate that such a multipole trap has attractive features for quantum computing and ultracold ion-atom collision studies.