A model of an open quantum system is presented in which irreversibility is introduced via boundary conditions on the Wigner function. The model is applied to the quantum-well resonant-tunneling diode. The calculations reproduce the negative-resistance characteristic of the device, and indicate that the tunneling current approaches steady state within a few hundred femtoseconds of a sudden change in applied voltage.

• Received 14 July 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.2853