Ultrafast coherent carrier control in quantum wells

We demonstrate femtosecond coherent control of excitons in quantum wells with phase-locked pairs of 100 fs infrared pulses. Co-polarised pulses allow control of exciton density and coherent destruction of excitons within a few hundred femtoseconds of their creation. Cross-polarised pulses yield coherent control of spin dynamics. Interference oscillations versus pulse separation yield a rich variety of quantum beats.