@article {2006, title = {An estimation of the controllability time for single-input systems on compact Lie Groups}, journal = {ESAIM Control Optim. Calc. Var. 12 (2006) 409-441}, year = {2006}, abstract = {Geometric control theory and Riemannian techniques are used to describe the reachable set at time t of left invariant single-input control systems on semi-simple compact Lie groups and to estimate the minimal time needed to reach any point from identity. This method provides an effective way to give an upper and a lower bound for the minimal time needed to transfer a controlled quantum system with a drift from a given initial position to a given final position. The bounds include diameters of the flag manifolds; the latter are also explicitly computed in the paper.}, doi = {10.1051/cocv:2006007}, url = {http://hdl.handle.net/1963/2135}, author = {Andrei A. Agrachev and Thomas Chambrion} }