Preparation and Determination of Spin-Polarized States in   Multi-Zeeman-sublevel Atoms
  We demonstrate a simple technique to prepare and determine the desired internal quantum states in multi-Zeeman-sublevel atoms. By choosing appropriate coupling and pumping laser beams, atoms can be easily prepared in a desired Zeeman sublevel with high purity or in any chosen ground-state population distributions. The population distributions or state purities of such prepared atomic states can be determined by using a weak, circularly-polarized probe beam due to differences in transition strengths among different Zeeman sublevels. Preparing well-defined internal quantum states in multi-Zeeman-sublevel atoms (or spin-polarized quantum-state engineering) will be very important in demonstrating many interesting effects in quantum information processing with multi-level atomic systems. 
Bo Wang, Yanxu Han, Jintao Xiao, Xudong Yang, Chunhong Zhang, Hai   Wang, Min Xiao, and Kunchi Peng