We show an equivalence between the approach of Buttiker and the Fermi quantum
stochastic calculus for mesoscopic systems. To illustrate the method we derive
the current fluctuations in a two terminal mesoscopic circuit with two tunnel
barriers containing a single quasi bound state on the well. The method enables
us to focus on either the incoming/outgoing Fermi fields in the leads, or on
the irreversible dynamics of the well state itself. The quantum stochastic
calculus we use is the Fermi analogue of the input/output methods of quantum
optics.Comment: 17 pages, 1 figur
