Ultrafast Gates for Single Atomic Qubits

We demonstrate single-qubit operations on a trapped atom hyperfine qubit using a single ultrafast pulse from a mode-locked laser. We shape the pulse from the laser and perform a pi rotation of the qubit in less than 50 ps with a population transfer exceeding 99% and negligible effects from spontaneous emission or ac Stark shifts. The gate time is significantly shorter than the period of atomic motion in the trap (Omega(Rabi)/nu(trap) > 10(4)), demonstrating that this interaction takes place deep within the strong excitation regime.