Controlling light on the nanoscale
in a similar way as electric
currents has the potential to revolutionize the exchange and processing
of information. Although light can be guided on this scale by coupling
it to plasmons, that is, collective electron oscillations in metals,
their local electronic control remains a challenge. Here, we demonstrate
that an individual quantum system is able to dynamically gate the
electrical plasmon generation. Using a single molecule in a double
tunnel barrier between two electrodes we show that this gating can
be exploited to monitor fast changes of the quantum system itself
and to realize a single-molecule plasmon-generating field-effect transistor
operable in the gigahertz range. This opens new avenues toward atomic
scale quantum interfaces bridging nanoelectronics and nanophotonics