Real-time dynamics of single-electron pumping

In this Letter, we study the real-ime dynamics of single-electron pumpings. We modulate the left tunneling barrier along with the dot level but slightly changing the right barrier to operate the single-electron pumping device at zero bias. We show the adiabatic to the non-adiabatic transition in pumping operations. We also find that the relation $I=e\omega \mathrm{/}2\pi$ is only valid in the low operating frequency adiabatic regime.