  Electron counting statistics of a current pump in an open system has
universal form in the weak pumping current regime. In the time domain, charge
transmission is described by two uncorrelated Poisson processes, corresponding
to electron transmission in the right and left direction. Overall noise is
super-poissonian, and can be reduced to poissonian by tuning the amplitude and
phase of driving signal so that current to noise ratio is maximized. Measuring
noise in this regime provides a new method for determining charge quantum in an
open system without any fitting parameters.
