The quantum optical Josephson interferometer

TL;DR

This paper proposes a quantum optical analog of a Josephson interferometer using coupled optical cavities with nonlinear interactions, revealing how dissipation and strong interactions influence Josephson oscillations and photon antibunching.

Contribution

It introduces a novel device model that maps to a Jaynes-Cummings system under strong interactions, exploring the suppression of Josephson oscillations via nonlinearity.

Findings

Josephson-like oscillations can be suppressed by increasing nonlinear coupling.

In the ultra-strong interaction limit, the system maps onto a Jaynes-Cummings model.

Photon antibunching indicates the transition to the nonlinear regime.

Abstract

The interplay between coherent tunnel coupling and on-site interactions in dissipation-free bosonic systems has lead to many spectacular observations, ranging from the demonstration of number-phase uncertainty relation to quantum phase transitions. To explore the effect of dissipation and coherent drive on tunnel coupled interacting bosonic systems, we propose a device that is the quantum optical analog of a Josephson interferometer. It consists of two coherently driven linear optical cavities connected via a central cavity with a single-photon nonlinearity. The Josephson-like oscillations in the light emitted from the central cavity as a function of the phase difference between two pumping fields can be suppressed by increasing the strength of the nonlinear coupling. Remarkably, we find that in the limit of ultra-strong interactions in the center-cavity, the coupled system maps on to an effective Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling strength. In the limit of a single nonlinear cavity coupled to two linear waveguides, the degree of photon antibunching from the nonlinear cavity provides an excellent measure of the transition to the nonlinear regime where Josephson oscillations are suppressed.