Tensor of coherences parameterization of multiqubit density operators and its use in detecting entanglement

The tensor of coherences is a real parameterization obtained by juxtaposition of affine Bloch vectors for multiqubit densities. The Stokes tensorial structure highlights pattern of classical and quantum correlations between subsystems. The tensorial formalism provides interpretation of NPT and bound entanglement corresponding to linear combinations of tensor products in which one of the factors is not well-defined density as its Bloch vector is very high. The explicit mixtures for families of separable states is feasible for few-qubit symmetric densities and provides evidence of entanglement for such densities.