We do modelling of quantum dots and open 2DEG systems, including thermal wavepackets, smooth walls and smooth disorder potentials, quantum point contacts and the effect of diffractive orbits (collaboration with Westervelt group), surface electron waves in an STM "quantum corral," including projecting a spin-polarized Kondo cloud by surface waves; scattering from modulated hard walls; magnetic effects in microstructures.

For instance, we have demonstrated experimentally the existence and significance of diffractive orbits in an open microwave billiard. Orbits that diffract off a sharp edge strongly influence the conduction spectrum, especially in the regime where there are no stable classical orbits. On resonance, the wave functions are influenced by both classical and diffractive orbits. Off resonance, the wave functions are determined by the constructive interference of multiple transient orbits. (Phys. Rev. Lett. **83**, 5342, (1999))

Comparison between theoretical quantum wavefunction (left) and experimentally measured microwave frequency shifts (right).