Observation of photon blockade in circuit QED using second-order correlation function measurements

Circuit quantum electrodynamics (QED) provides an attractive platform to effectively study photon-photon interactions mediated by their strong and resonant coupling to a superconducting qubit embedded into a transmission line resonator. Driving the coupled system with a coherent microwave frequency tone the anharmonicity of the Jaynes-Cummings ladder blocks the transmission of more than a single photon through the resonator at a time. Using on-chip microwave beam splitters, linear amplifiers, and quadrature amplitude detectors we observe fluorescence and Rayleigh scattering in Mollow-triplet-like spectra. We investigate the phenomenon of photon blockade in second-order correlation function measurements which show antibunching and signatures of Rabi oscillations induced by the continuous drive coupling the ground and first excited states of the Jaynes-Cummings ladder.