Necessary and sufficient conditions for the freezing phenomena of quantum discord under phase damping
Bo You, Li-Xiang Cen · Physical Review A · 2012
We investigate the freezing phenomenon of quantum discord occurring in phase damping noise processes. By relating the expression of the time variation of the discord to the convex function of relative entropy, we obtain the necessary and sufficient conditions of the phenomenon for standard Bell-diagonal states. These conditions are applicable also to the phenomenon occurring in a non-Markovian dephasing process. Moreover, we show that the same condition and phenomenon coincide in an unusual sort of Bell-diagonal states beyond the standard form.