  Edge magnetoplasmon is an emergent chiral bosonic mode promising for studying
electronic quantum optics. While the plasmon transport has been investigated
with various techniques for decades,its coupling to a mesoscopic device
remained unexplored. Here, we demonstrate the coupling between a single plasmon
mode in a quantum Hall plasmon resonator and a double quantum dot (DQD).
Resonant plasmon-assisted tunneling is observed in the DQD through absorbing or
emitting plasmons stored in the resonator. By using the DQD as a spectrometer,
the plasmon energy and the coupling strength are evaluated, which can be
controlled by changing the electrostatic environment of the quantum Hall edge.
The observed plasmon-electron coupling encourages us for studying strong
coupling regimes of plasmonic cavity quantum electrodynamics.
