Microwave spectroscopy on a double quantum dot with an on-chip Josephson oscillator

We present measurements on microwave spectroscopy on a double quantum dot w ith an on-chip microwave source. The quantum dots are realized in the two-d imensional electron gas of an AlGaAs/GaAs heterostructure and are weakly co upled in series by a tunnelling barrier forming an 'ionic' molecular state. We employ a Josephson oscillator formed by a long Nb/Al-AlOx/Nb junction a s a microwave source. We find photon-assisted tunnelling sidebands induced by the Josephson oscillator, and compare the results with those obtained us ing an externally operated microwave source.