The quantum optical Josephson interferometer

The photon-blockade effect, where nonlinearities at the single-photon level alter the quantum statistics of light emitted by an optical cavity, has been observed in cavity quantum electrodynamics experiments with atomic and solid-state systems. Motivated by the success of single-cavity quantum electrodynamics experiments, the focus has recently shifted to the exploration of the rich physics promised by strongly cor8 related quantum-optical systems in multicavity and extended photonic media. Even though most cavity quantum electrodynamics structures are inherently dissipative, the majority of the early works on strongly correlated photonic systems have assumed cavity structures where losses are essentially negligible. Here we investigate a dissipative quantum-optical system that consists of two coherently driven linear optical cavities connected through a central cavity with a single-photon nonlinearity (an optical analogue of the Josephson interferometer). Strong photonic correlations can be identified through the suppression of Josephson-like oscillations of the light emitted from the central cavity as the nonlinearity is increased. In the limit of a single nonlinear cavity coupled to two linear waveguides, photon-correlation measurements should provide a unique probe of the crossover to the strongly correlated regime. The interplay between coherent tunnel coupling and on-site interactions in dissipation-free bosonic