Self-referenced single-electron quantized current source.

The future redefinition of the international system of units in terms of natural constants requires a robust, high-precision quantum standard for the electrical base unit ampere. However, the reliability of any single-electron current source generating a nominally quantized output current I=ef by delivering single electrons with charge e at a frequency f is eventually limited by the stochastic nature of the underlying quantum mechanical tunneling process. We experimentally explore a path to overcome this fundamental limitation by serially connecting clocked single-electron emitters with multiple in situ single-electron detectors.

Counting statistics for electron capture in a dynamic quantum dot.

We report noninvasive single-charge detection of the full probability distribution P(n) of the initialization of a quantum dot with n electrons for rapid decoupling from an electron reservoir. We analyze the data in the context of a model for sequential tunneling pinch-off, which has generic solutions corresponding to two opposing mechanisms. One limit considers sequential "freeze-out" of an adiabatically evolving grand canonical distribution, the other one is an athermal limit equivalent to the solution of a generalized decay cascade model.