  The recent developments of electron quantum optics in quantum Hall edge
channels have given us new ways to probe the behavior of electrons in quantum
conductors. It has brought new quantities called electronic coherences under
the spotlight. In this paper, we explore the relations between electron quantum
optics and signal processing through a global review of the various methods for
accessing single- and two-electron coherences in electron quantum optics. We
interpret electron quantum optics interference experiments as analog signal
processing converting quantum signals into experimentally observable quantities
such as current averages and correlations.
  This point of view also gives us a procedure to obtain quantum information
quantities from electron quantum optics coherences. We illustrate these ideas
by discussing two mode entanglement in electron quantum optics. We also sketch
how signal processing ideas may open new perspectives for representing
electronic coherences in quantum conductors and understand the properties of
the underlying many-body electronic state.
