Conductance of Fabry-Pérot and two-slit electronic waveguides

We study the quantum-mechanical ballistic propagation of a two-dimensional noninteracting electron gas within waveguide structures similar to a Fabry-Pérot interferometer and to the Young two-slit interference structure. The novel features in the Fabry-Pérot setup are the following: (1) possibility of tuning the conductance to very small values; (2) universal conductance fluctuations (in ballistic propagation) of order 2e2/h (which are characteristic of disordered systems); (3) approximate periodicity of the conductance as a function of geometrical parameters, in agreement with a recent experiment. In the two-slit configuration, the structure of both the conductance and the intensity is not similar to the optical Young interference pattern (due to the presence of reflecting walls on all sides) and, quite surprisingly, may show a minimum at the center of the waveguide.