Conditions for the freezing phenomena of geometric measure of quantum   discord for arbitrary two-qubit X states under non-dissipative dephasing   noises
  We study the dynamics of geometric measure of quantum discord (GMQD) under the influences of two local phase damping noises. Consider the two qubits initially in arbitrary X-states, we find the necessary and sufficient conditions for which GMQD is unaffected for a finite period. It is further shown that such results also hold for the non-Markovian dephasing process. 
Wei Song, Zhuo-Liang Cao
quant-ph