Controllability of multi-partite quantum systems and selective   excitation of quantum dots
  We consider the degrees of controllability of multi-partite quantum systems as well as necessary and sufficient criteria for each case. The results are applied to the problem of simultaneous control of an ensemble of quantum dots with a single laser pulse. Finally, we apply optimal control techniques to demonstrate selective excitation of individual dots for a simultaneously controllable ensemble. 
Sonia G Schirmer, Ivan C H Pullen, Allan I Solomon