Towards quantum information with trapped calcium ions

Ground state cooling and coherent manipulation of ions in a rf-(Paul) trap is the prerequisite for quantum information experiments with trapped ions. In our experiments a single ⁴⁰Ca⁺ ion in a conventional Paul trap has been cooled to the ground state of vibration with 99.9% (98%) probability in the axial (radial) trap direction, We use a continuous resolved sideband method where we drive the S_1/2-D_5/2 quadrupole transition (@729 nm) and repump the ion to the ground state via the D_5/2-P_3/2 dipole transition. Efficient cooling is achieved on the timescale of a few ms