  A novel method of coherent manipulation of the electron tunneling in
quantum-dots is proposed, which utilizes the quantum interference in
nonadiabatic double-crossing of the discrete energy levels. In this method, we
need only a smoothly varying gate voltage to manipulate electrons, without a
sudden switching-on and off. A systematic design of a smooth gate-pulse is
presented with a simple analytic formula to drive the two-level electronic
state to essentially arbitrary target state, and numerical simulations for
complete transfer of an electron is shown for a coupled double quantum-dots and
an array of quantum-dots. Estimation of the manipulation-time shows that the
present method can be employed in realistic quantum-dots.

Mesoscale and Nanoscale Physics;Materials Science