@article {2005, title = {Time minimal trajectories for two-level quantum systems with drift}, number = {SISSA;5/2005/M}, year = {2005}, abstract = {On a two-level quantum system driven by an external field, we consider the population transfer problem from the first to the second level, minimizing the time of transfer, with bounded field amplitude. On the Bloch sphere (i.e. after a suitable Hopf projection), this problem can be attacked with techniques of optimal syntheses on 2-D manifolds.}, url = {http://hdl.handle.net/1963/1688}, author = {Ugo Boscain and Paolo Mason} }