Quantum interference in transistors

We consider adiabatic charge transport through transistor based on quantum dot caused by two periodically changing external perturbations. Both the magnitude and the sign of the transmitted charge are extremely sensitive to the configuration of the transistor and to the magnetic field. We find the correlation function characterizing the random value of this pumped charge for arbitrary strength of perturbation. In contrast to previous theoretical and experimental claims, the charge is found not to have any symmetry with respect to the inversion of magnetic field. At strong pumping perturbation, the variance of the charge , <Q²> is found to be proportional to the length of the contour in parametric space.