  We explore the microwave radiation emitted from a biased double quantum dot
due to the inelastic tunneling of single charges. Radiation is detected over a
broad range of detuning configurations between the dot energy levels with
pronounced maxima occurring in resonance with a capacitively coupled
transmission line resonator. The power emitted for forward and reverse resonant
detuning is found to be in good agreement with a rate equation model, which
considers the hybridization of the individual dot charge states.
