A self-referenced single-electron current source

A current source based on clocked single electron transfer is the natural candidate for the realization of the SI base unit ampere following a future redefinition by a fixed value of the elementary charge e. However, the single electron transfer relies on quantum mechanical tunneling and thus is of inherent stochastic nature. This leads to small deviations of the actual current from the nominal value. Here we experimentally demonstrate in-situ accounting of such deviations and thereby reduce the uncertainty in output current of our device by a factor of 50.