Transport in quantum devices: Modelling contacts in the Wigner formalism

We shall discuss the role of the contacts as they are modelled in the conventional treatment of quantum devices based on the Wigner-Function formalism. Our analysis will show that the artificial spatial separation between device active region and external reservoirs is intrinsically incompatible with the non-local character of quantum mechanics. More specifically, by means of an exactly-solvable semiconductor model, we shall show that the application of the usual Up-Wind boundary scheme to the Wigner transport equation may produce highly non-physical results, like boundary-driven negative probability distributions.