Towards Quantum Computation with Trapped Calcium Ions

Abstract

For quantum information experiments we have cooled one and two ⁴⁰Ca⁺ions to the ground state of vibration with up to 99.9% probability, using resolved sideband cooling on the optical S_1/2-D_5/2 quadrupole transition. Implementing a novel cooling scheme based on electromagnetically induced transparency on the S_↓/2 -P_↓/2 manifold we have achieved simultaneous ground state cooling of two motional sidebands 1.7 MHz apart. Coherent quantum state manipulation on the S_1/2 -D_5/2 quadrupole transition at 729 nm was demonstrated and up to 30 Rabi oscillations within 1.4 ms have been observed starting from the motional ground state and from the n=1 Fock state. In a linear rf-trap two ions were cooled to the ground state of motion and individual addressing of the ions with laser pulses is achieved.