Dissipative Josephson effect in coupled nanolasers

TL;DR

This paper explores how dissipative interactions in coupled nanolasers can amplify a photonic Josephson current, leading to a non-equilibrium phase transition and potential applications in quantum-optical interferometry.

Contribution

It introduces a model of coupled nanolasers with dissipative interactions, revealing a dissipation-enhanced Josephson effect and phase transition in a non-equilibrium setting.

Findings

Identification of a non-equilibrium phase transition between phase-locked and non-phase-locked states.

Demonstration that the Josephson photocurrent can measure optical phase differences.

Show that interferometric sensitivity improves with photon number and incoherent pumping rate.

Abstract

Josephson effects are commonly studied in quantum systems in which dissipation or noise can be neglected or do not play a crucial role. In contrast, here we discuss a setup where dissipative interactions do amplify a photonic Josephson current, opening a doorway to dissipation-enhanced sensitivity of quantum-optical interferometry devices. In particular, we study two coupled nanolasers subjected to phase coherent drivings and coupled by a coherent photon tunneling process. We describe this system by means of a Fokker-Planck equation and show that it exhibits an interesting non-equilibrium phase diagram as a function of the coherent coupling between nanolasers. As we increase that coupling, we find a non-equilibrium phase transition between a phase-locked and a non-phase-locked steady-state, in which phase coherence is destroyed by the photon tunneling process. In the coherent, phase-locked regime, an imbalanced photon number population appears if there is a phase difference between the nanolasers, which appears in the steady-state as a result of the competition between competing local dissipative dynamics and the Josephson photo-current. The latter is amplified for large incoherent pumping rates and it is also enchanced close to the lasing phase transition. We show that the Josephson photocurrent can be used to measure optical phase differences. In the quantum limit, the accuracy of the two nanolaser interferometer grows with the square of the photon number and, thus, it can be enhanced by increasing the rate of incoherent pumping of photons into the nanolasers.