Ultrafast coherent excitation of a 40Ca+ ion

Fast entangling quantum gates can significantly enhance the performance of a trapped-ion quantum computer. In pursuit of implementing a fast two-qubit gate, we investigate the coherent excitation of a ⁴⁰Ca⁺ ion with a train of picosecond pulses resonant to the 4S_1/2 ≤ftrightarrow 4P_3/2 transition. The optical pulse train is derived from a mode-locked, stabilized optical frequency comb. We implement two techniques to characterize the pulse-ion interaction and show how all requirements can be met for an implementation of a fast phase gate operation.