  Using the information geometry approach, we determine the volume of the set
of two-qubit states with maximally disordered subsystems. Particular attention
is devoted to the behavior of the volume of sub-manifolds of separable and
entangled states with fixed purity. We show that the usage of the classical
Fisher metric on phase space probability representation of quantum states gives
the same qualitative results with respect to different versions of the quantum
Fisher metric.
