Accurate measurement of currents generated by single electrons transportedin a one-dimensional channel

The acoustoelectric current generated by the transport of single electrons using surface acoustic waves through a one-dimensional channel offers the p ossibility of realising a quantum standard of current based on the electron ic charge e. At NPL a measurement system using a commercial electrometer ha s been developed for investigating the flatness and accuracy of the constan t current plateaux with an uncertainty of 15fA. Also a new instrument, base d on a cryogenic current comparator (CCC), has been developed with which it is expected that a relative accuracy of 1fA/nA can be achieved. The author s present preliminary measurements of the quantised current using the elect rometer and an experimental arrangement for resolving the 'metrological tri angle' using the CCC.