Ultrafast optical manipulation of single electron spins in quantum dots

Most schemes for quantum information processing require fast single qubit operations as well as initialization and read-out steps. Here we describe recent experimental realizations of schemes for time-resolved initialization, coherent control, and read-out of a single electron spin state in an individual quantum dot using all-optical techniques. The spin state is manipulated via the optical Stark effect using off-resonant, picosecond-scale optical pulses. The coherent rotation of a single electron spin state through arbitrary angles up to ππ radians is demonstrated, constituting a single qubit gate. This spin manipulation is directly monitored using time-resolved Kerr rotation spectroscopy allowing for the observation of the coherent evolution of a single electron spin state in time as well as revealing the spin lifetime and gg-factor.