Robust state preparation of a single trapped ion by adiabatic passage

We report adiabatic passage experiments with a single trapped ion. By applying a frequency-chirped laser pulse with a Gaussian amplitude envelope, we reach a transfer efficiency of 0.99(1) on an optical transition from the electronic ground state S1/2 to the metastable state D5/2. This transfer method is shown to be insensitive to the accurate setting of laser parameters, and therefore is suitable as a robust tool for ion-based quantum computing.