Compressibility measurements using a circuit QED architecture

Quantum dots exhibit a wide variety of many body phenomena. A circuit QED architecture could also be instrumental for understanding them because it allows one to directly probe the compressibility of an electronic system. One of the most paradigmatic phenomenon is the Kondo effect which is at the heart of many electron correlation effects. We will show that a circuit QED architecture has allowed us to observe the decoupling of spin and charge excitations in a Kondo system. The Kondo resonance, visible in the conductance of the quantum dot, is 'transparent' to the microwave cavity photons. This reveals the freezing of charge dynamics. Our setup could be generalized to other types of mesoscopic circuits with many-body correlations and used to perform quantum simulation of fermion-boson systems.