  We consider theoretically an electronic Mach-Zehnder interferometer
constructed from quantum Hall edge channels and quantum point contacts, fed
with single electrons from a dynamic quantum dot source. By considering the
energy dependence of the edge-channel guide centres, we give an account of the
phase averaging in this set up that is particularly relevant for the short,
high-energy wavepackets injected by this type of electron source. We present
both analytic and numerical results for the energy-dependent arrival time
distributions of the electrons and also give an analysis of the delay times
associated with the quantum point contacts and their effects on the
interference patterns. A key finding is that, contrary to expectation, maximum
visibility requires the interferometer arms to be different in length, with an
offset of up to a micron for typical parameters. By designing interferometers
that incorporate this asymmetry in their geometry, phase-averaging effects can
be overcome such that visibility is only limited by other incoherent
mechanisms.
