Verification of polarization selection rules and implementation of   selective coherent manipulations of hydrogenic transitions in n-GaAs
  Electrons bound to shallow donors in GaAs have orbital energy levels analogous to those of the hydrogen atom. The polarization selection rules for optical transitions between the states analogous to the 1s and 2p states of hydrogen in a magnetic field are verified using Terahertz (THz) radiation from the UCSB Free Electron Laser. A polarization-selective coherent manipulation of the quantum states is demonstrated and the relevance to quantum information processing schemes is discussed. 
M. F. Doty, B. T. King, M. S. Sherwin, and C. R. Stanley