Quantum phase transitions of light

TL;DR

This paper proposes a photonic system of coupled cavities with embedded atoms that can exhibit quantum phase transitions, such as from Mott insulator to superfluid, enabling new quantum many-body experiments and devices.

Contribution

It introduces a novel strongly interacting photonic system using cavity-atom setups that can realize and observe quantum phase transitions like Mott insulator to superfluid.

Findings

Predicts a Mott insulator to superfluid transition in the proposed system.

Identifies feasible experimental platforms such as diamond NV centers and superconducting resonators.

Shows potential for quantum simulation and device applications.

Abstract

Recently, condensed matter and atomic experiments have reached a length-scale and temperature regime where new quantum collective phenomena emerge. Finding such physics in systems of photons, however, is problematic, as photons typically do not interact with each other and can be created or destroyed at will. Here, we introduce a physical system of photons that exhibits strongly correlated dynamics on a meso-scale. By adding photons to a two-dimensional array of coupled optical cavities each containing a single two-level atom in the photon-blockade regime, we form dressed states, or polaritons, that are both long-lived and strongly interacting. Our zero temperature results predict that this photonic system will undergo a characteristic Mott insulator (excitations localised on each site) to superfluid (excitations delocalised across the lattice) quantum phase transition. Each cavity's impressive photon out-coupling potential may lead to actual devices based on these quantum many-body effects, as well as observable, tunable quantum simulators. We explicitly show that such phenomena may be observable in micro-machined diamond containing nitrogen-vacancy colour centres and superconducting microwave strip-line resonators.