Coherent manipulation of a single electron surfing on a sound wave

Surface acoustic waves (SAW) provide a promising platform to realize quantum optics experiments with electrons at the single particle level. Earlier single shot experiments have shown SAW-assisted electron transport between spatially separated quantum dots over a distance of 4 µm with an efficiency of about 92 % [1]. Here we go an important step further. We couple two quantum channels by a tunnel barrier along a region of 2 µm. At the ends of each channel respectively a quantum dot is placed serving as single electron source and detector. We demonstrate single electron transport over a distance of 22 µm with extremely high efficiency above 99 %. Changing the energy detuning in the coupling region we can partition the electron on-demand into two paths. By gradually changing the barrier height we additionally observe tunnel oscillations of the probability that the electron ends up at the upper or the lower detector quantum dot. This finding demonstrates coherent manipulation of the electron quantum state on the fly. Our results pave the way for the implementation of a solid state flying qubit having high relevance in fundamental research and quantum information technology.

[1] S. Hermelin et al., Nature (2011)