Nonadiabatic electron manipulation in quantum dot arrays

A 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 an arbitrary target state, and numerical simulations for complete transfer of an electron is shown for 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.

Figure 1

Schematic picture of time dependence of energies of dots. The solid lines are the energies of two dots, and the dashed lines are the eigenvalues.

Figure 2

The probabilities $P_1\left(t\right)$ and $P_2\left(t\right)$ are shown as a function of time. In the inset, the time dependences of eigenenergies are also shown. The unit of time is $\hslash ∕meV\simeq 4.14\times {10}^{-13}\mathrm{s}$.

Figure 3

Global control by an oscillating electric field. (a) Schematic picture of time dependence of the staggered dots model. (b) The probability finding electron in each dot is shown as a function of time.