Polarization-gradient cooling of 1D and 2D ion Coulomb crystals

Abstract

We present experiments on polarization gradient cooling of Ca ^+ multi-ion Coulomb crystals in a linear Paul trap. Polarization gradient cooling of the collective modes of motion whose eigenvectors have overlap with the symmetry axis of the trap is achieved by two counter-propagating laser beams with mutually orthogonal linear polarizations that are blue-detuned from the S _1/2 ↔ P _1/2 transition. We demonstrate cooling of linear chains of up to 51 ions and 2D-crystals in zig-zag configuration with 22 ions. The cooling results are compared with numerical simulations and the predictions of a simple model of cooling in a moving polarization gradient.

Keywords

• trapped ions
• ion crystals
• laser cooling
• polarization gradient cooling
• quantum simulation