Single-electron source with a quantum Hall edge state

Electron quantum optics has been developed based on the wave nature of electrons in various solid-state devices such as GaAs/AlGaAs and graphene. The coherent manipulation of individual electrons in a single electron level could lead another qubit platform, corresponding to the path qubit with single photons. To the end, a coherent on-demand single-electron source is necessary. In this talk, I will introduce a single-electron source based on a quantum dot with a finite changing energy and quantum Hall edge state. When we drove the quantum dot by an AC gate voltage, it absorbs electrons, leaving a hole in the edge channel and successively emits electrons into the same channel with the modulation of the AC voltage. With an energy barrier in the edge channel, we successfully separated the emitted electrons and holes, leading to a rectified single-electron current satisfying a relation of I = −ef, where e is the elementary charge and f is the frequency of the AC drive. In the energy spectroscopy with the energy barrier, we observed that the energy distribution of the single electrons showed only ~5 meV at a 40 meV-energy level, contrary to a ~23 meV broadening at the same level for a conventional tunable-barrier quantum dot. Thus, we believe that our newly developed single-electron source could be useful to find a coherence of electrons at a few-tens meV level.