Circuit models for small signal performance of nanodevices based on two-state quantum systems

Nanodevices are microsystems governed by the laws of quantum mechanics embedded in a macroscopic environment governed by the laws of classical electrodynamics. Their use as components in nanocircuits ultimately requires a description in terms of electrical quantities, voltages and currents or incident and reflected electromagnetic waves, present at some properly defined electrical ports. Thus the quantum performance has to be pictured in terms of such quantities, i.e. by equivalent circuits. These are used in this paper to model the passive and the active small signal performance of nanodevices based on two-state quantum systems interacting with the classical electromagnetic environment and a thermal bath.