  Precise control over interactions between ballistic electrons will enable us
to exploit Coulomb interactions in novel ways, to develop high-speed sensing,
to reach a non-linear regime in electron quantum optics and to realise schemes
for fundamental two-qubit operations on flying electrons. Time-resolved
collisions between electrons have been used to probe the indistinguishability,
Wigner function and decoherence of single electron wavepackets. Due to the
effects of screening, none of these experiments were performed in a regime
where Coulomb interactions were particularly strong. Here we explore the
Coulomb collision of two high energy electrons in counter-propagating ballistic
edge states. We show that, in this kind of unscreened device, the partitioning
probabilities at different electron arrival times and barrier height are shaped
by Coulomb repulsion between the electrons. This prevents the wavepacket
overlap required for the manifestation of fermionic exchange statistics but
suggests a new class of devices for studying and manipulating interactions of
ballistic single electrons.
