01375nas a2200109   4500008004300000245010700043210006900150260003000219520095800249100002201207856003601229       2004                        en_Ud  00aTensor of coherences parametrization of multiqubit density operators for entanglement characterization0 aTensor of coherences parametrization of multiqubit density opera  bAmerican Physical Society3 aFor multiqubit densities, the tensor of coherences (or Stokes tensor) is a real parameterization obtained by the juxtaposition of the affine Bloch vectors of each qubit. While it maintains the tensorial structure of the underlying space, it highlights the pattern of correlations, both classical and quantum, between the subsystems and, due to the affine parameterization, it contains in its components all reduced densities of all orders. The main purpose of our use of this formalism is to deal with entanglement. For example, the detection of bipartite entanglement is straightforward, as it is the synthesis of densities having positive partial transposes between desired qubits. In addition, finding explicit mixtures for families of separable states becomes a feasible issue for few qubit symmetric densities (we compute it for Werner states) and, more important, it provides some insight on the possible origin of entanglement for such densities.1 aAltafini, Claudio  uhttp://hdl.handle.net/1963/2845