Emergent phases of light in driven-dissipative lattices

Matteo Biondi
ETH Zurich, Switzerland

Quantum engineered cavity/circuit QED architectures provide platforms for exploring strongly correlated photons with light-matter induced interactions. These systems are typically described by the nonequilibrium Bose-Hubbard model. In this talk, I will focus on two beautiful examples of the emergent physics of strongly interacting photons in cavity arrays. In the first part, we will see how the phase diagram of a driven-dissipative photonic lattice can be theoretically characterized in terms of a classical gas-liquid transition, where the location of the critical point is modulated by the quantum nature of photons. Quantum trajectories show synchronised dynamics as a microscopic manifestation of this photonic gas-liquid transition in the time domain. In the second part, I will discuss how to engineer strongly-correlated phases of light by quenching the kinetic energy through frustration. This pushes the system towards an incompressible state of light characterized by short-ranged density-wave order. I will then show how a truly ordered phase can emerge in this frustrated system making use of pump design. These works provide a timely connection with ongoing experiments on circuit QED lattices and exciton-polariton fluids.