This scanning electron micrograph shows an electrostatic “split” gate that controls the passage of a single electron on a liquid helium surface from one electron reservoir to another. Liquid helium is condensed on the flat bed and electrons flow along the top surface of the condensed helium. (Inset: A close-up of the split gate.) Bradbury et al. use an array of gates to detect and control the transport of single electrons on a liquid helium surface operated under the same principle.