Probing quantum electromagnetic magnetic fields with subnanosecond time resolution: the single electron radar

In this talk we discuss how an electronic interferometer can be used to measure a time dependent electric field on a sub-nanosecond time scale based on alteration of the wave function of a single electronic excitation propagating across a Mach-Zenhder interferometer when the fast varying potential is appied to one of the two branches, thereby realizing the electronic analogue of a radar.

Our key result is the electron radar equation that connects the experimental signal — the Aharonov-Bohm dependent part of the finite frequency average outgoing current — to the electronic wave function used as a probe and to the electromagnetic field to be probed. It is valid in the presence of Coulomb interactions within the interferometer and quantum lectromagnetic field and incorporates the back-action effects of the quantum electromagnetic field to be probed onto the electron fluid. The detection of a squeezed vacuum which exhibits time dependent quantum fluctuations will be used as an illustration of this general framework.