Maintenance of Coherence and Polarization Evolution in a Supersymmetric   Multiphoton Model
  The elimination of decoherence of two-state quantum systems interacting with a thermal reservoir through an external controllable driving field is discussed in the present paper. The restriction equation with which the external controllable driving field should agree will be derived. Based on this, we obtain the time-development equation of the off-diagonal elements of density operator in the supersymmetric multiphoton two-state quantum systems, which is helpful for studying the polarization evolution in this two-state quantum model. 
Jian Qi Shen & Zhi Chao Ruan