  A hallmark of quantum control is the ability to manipulate quantum emission
at the nanoscale. Through scanning tunneling microscopy induced luminescence
(STML) we are able to generate plasmonic light originating from inelastic
tunneling processes that occur in a few-nanometer thick molecular film of
C$_{60}$ deposited on Ag(111). Single photon emission, not of excitonic origin,
occurs with a 1/$e$ lifetime of a tenth of a nanosecond or less, as shown
through Hanbury Brown and Twiss photon intensity interferometry. We have
performed tight-binding calculations of the electronic structure for the
combined Ag-C$_{60}$-tip system and obtained good agreement with experiment.
The tunneling happens through electric field induced split-off states below the
C$_{60}$ LUMO band, which leads to a Coulomb blockade effect and single photon
emission. The use of split-off states is shown to be a general technique that
has special relevance for narrowband materials with a large bandgap.
