  We report an experimental technique to measure and manipulate the
arrival-time and energy distributions of electrons emitted from a semiconductor
electron pump, operated as both a single-electron source and a two-electron
source. Using an energy-selective detector whose transmission we control on
picosecond timescales, we can measure directly the electron arrival-time
distribution and we determine the upper-bound to the distribution width to be
30 ps. We study the effects of modifying the shape of the voltage waveform that
drives the electron pump, and show that our results can be explained by a
tunneling model of the emission mechanism. This information was in turn used to
control the emission-time difference and energy gap between a pair of
electrons.
