Quantum sensing of time dependent electromagnetic fields with single electron excitations

Characterizing quantum states of the electromagnetic field at microwave frequencies requires fast and sensitive detectors capable of simultaneously probing both the field's time-dependent amplitude and its quantum fluctuations. In this presentation, we explore the potential of single-electron excitations propagating in electronic interferometers, such as Mach-Zehnder or Fabry-Perot, to probe the quantum state of electromagnetic radiation with sub-nanosecond precision. We discuss how information about the electromagnetic field's quantum state is encoded in the interference contribution to the average outgoing electrical current. As an example, we explain how a single-electron wave packet can detect sub-vacuum fluctuations (squeezing) of microwave radiation. Finally, we present the realization of a quantum sensor that exploits the phase of a single-electron wavefunction to detect a classical time-dependent electromagnetic field with a few microwave photons resolution, paving the way for on-chip detection of quantum radiation, including squeezed and Fock states.