Ballistic transport in a disordered environment: Why is conductance quantization observable?

Abstract
We consider transport in a quantum-coherent system containing a ballistic region and disordered reservoirs connected to it. The ballistic region works as a filter: It suppresses conductance fluctuations that are due to disorder and recovers conductance quantization. However, the suppression is much weaker than that predicted by Ohm’s law for classical resistors in series.