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has z -directional Bloch vectors and its correlation vector changes from ( g$_{1}$, g$_{2}$, g$_{3}$ ) to ( − g$_{3}$, g$_{2}$, g$_{1}$ ). Similarly, one can change the state with y -directional Bloch vectors into the state with z -directional Bloch vectors without altering the diagonal property of the correla- tion term. 

In this reason it is reasonable to assume that the directions of the Bloch vectors are z -direction by writing r = (0 , 0 , r ) and s = (0 , 0 , s ) $^{4}$. In this case the arbitrary two-qubit 

