Suppression of shot noise in metallic diffusive conductors

The shot-noise power in a disordered phase-coherent conductor, much longer than the mean free path but much shorter than an inelastic scattering length, is one-third of the classical value of a Poisson process. The reduction below the classical value is a consequence of noiseless open quantum channels. In conductors much longer than an inelasic length, shot noise is further suppressed due to counterbalancing voltage fluctuations which enforce charge neutrality.