Coherent manipulation of single electron spins with Landau-Zener sweeps

We propose a novel method to manipulate the state of a single electron spin in a semiconductor quantum dot (QD). The manipulation is achieved by tunnel coupling a QD, labeled $L$, and occupied with an electron to an adjacent QD, labeled $R$, which is not occupied by an electron but having an energy linearly varying in time. We identify a parameter regime in which a complete population transfer between the spin eigenstates $|L\uparrow\rangle$ and $|L\downarrow\rangle$ is achieved without occupying the adjacent QD. This method is convenient due to the fact that manipulation can be done electrically, without the precise knowledge of the spin resonance condition, and is robust against Zeeman level broadening caused by nuclear spins.