  The quantized current generated by a quantum dot pump is calculated
numerically. The numerical simulation is done by dividing the time varying
potential into many static potentials with a short time interval and
calculating the electron capture and pumping rate with the time independent
Schrodinger equation. The simulation results show good agreement with reported
experimental results qualitatively. The calculated 2D pump current map and the
plateau width dependence on the modulation gate voltage show good agreement
with the experimental results. From the simulation results, it is explained how
the back-tunneling process affects the accuracy of the current plateaus
quantitatively. Also, the energy distribution of the pumped electron is
calculated, which can be measured experimentally. Finally, it is found that the
pump current accuracy can be enhanced by increasing the entrance gate width,
which is important to realize the quantum current standard.
