In this paper we give an explicit parametrization for all two qubit densitymatrices. This is important for calculations involving entanglement and manyother types of quantum information processing. To accomplish this we present ageneralized Euler angle parametrization for SU(4) and all possible two qubitdensity matrices. The important group-theoretical properties of such adescription are then manifest. We thus obtain the correct Haar (Hurwitz)measure and volume element for SU(4) which follows from this parametrization.In addition, we study the role of this parametrization in the Peres-Horodeckicriteria for separability and its corresponding usefulness in calculatingentangled two qubit states as represented through the parametrization.
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