  Engineering and studying few-electron states in ballistic conductors is a key
step towards understanding entanglement in quantum electronic systems. In this
Letter, we introduce the intrinsic two-electron coherence of an electronic
source in quantum Hall edge channels and relate it to two-electron
wavefunctions and to current noise in an Hanbury Brown--Twiss interferometer.
Inspired by the analogy with photon quantum optics, we propose to measure the
intrinsic two-electron coherence of a source using low-frequency current
correlation measurements at the output of a Franson interferometer. To
illustrate this protocol, we discuss how it can distinguish between a time-bin
entangled pure state and a statistical mixture of time shifted electron pairs.
