Measurement of the nonadiabatically-induced coherent time evolution of a single-electron wavefunction in a surface acoustic wave dynamic quantum dot

Observation of coherent single-electron dynamics is severely limited by experimental bandwidth. We present a method to overcome this using moving quantum dots defined by surface acoustic waves. Each dot holds a single electron, and travels through a static potential landscape. When the dot moves abruptly between regions of different confinement, the electron is excited into a superposition of states, and oscillates unitarily from side to side. These oscillations are measured almost non-invasively, by allowing a small amount of tunnelling out of the dot each time the wavefunction approaches a tunnel barrier. We have modelled this in detail by solving the single-particle time-dependent Schr\"odinger equation for a realistic potential, and find good agreement between the measurements and the simulations.