Two-electron coherence and its measurement in electron quantum optics

International audienceEngineering and studying few-electron states in ballistic conductors is a key step towards understanding entanglement in quantum electronic systems. In this Rapid Communication, we introduce the intrinsic two-electron coherence of an electronic source in quantum Hall edge channels and relate it to two-electron wave functions and to current noise in a 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