USING THE WIGNER FUNCTION FOR QUANTUM TRANSPORT IN DEVICE SIMULATION

The Wigner function was introduced as a generalization of the concept of distribution function for quantum statistics. The aim of this work is pushing further the formal analogy between quantum and classical ap proaches. The Wigner function is defined as an ensemble average, i.e., in terms of a mixture of pure states. From the point of view of basic physics, it would be very appealing to be able to define a Wigner fun ction also for pure states and the associated expectation values for q uantum observables, in strict analogy with the definition of mean valu e of a physical quantity in classical mechanics; then correct results for any quantum system should be recovered as appropriate superpositio ns of such ''pure-state'' quantities. We will show that this is actual ly possible, st the cost of dealing with generalized functions in plac e of proper functions.