Mott Insulator Transition in a Quantum Fluid of Light

Photons are great carriers of information but they usually don’t interact with one another.

Atoms interact but are hard to manipulate and do not benefit from the toolbox of quantum optics for detecting quantum fluctuations and entanglement.Many approaches have been proposed to marry these two systems for quantum simulation of condensed matter with strongly interacting photons, but to date, the realization of large-scale synthetic materials made of optical photons is still missing.My project targets this exciting goal, namely the creation of synthetic photonic matter.

It relies on the original approach of engineering a quantum phase transition in a fluid of light.Specifically, I will investigate the superfluid to Mott insulator transition for light propagating in a dense cold atomic cloud.

Photons will acquire an effective mass due to the paraxial approximation and I will generate and tune the strong photon-photon interactions via a giant Kerr non-linearity induced by manipulating atomic coherences.

In this regime, photons will behave as a quantum fluid of light and follow an evolution similar to ultracold atomic quantum gases.My original hypothesis is that a fluid of light should undergo the same phase transition, driven by quantum fluctuations, as quantum gases do, and that a many-body state of light will emerge from this transition.At the fundamental level, a Mott insulator state of light allows for exploring truly quantum effects such as the emergence of analogue of phase transition in non-equilibrium systems, the presence of quantum depletion and pre-thermal states and the entanglement dynamics in many-body systems.On the applied side, a photonic Mott insulator is a giant source of single photons (or any Fock state) with potentially several hundreds of lattice sites delivering tunable photon number-states in parallel.

It will be a game changer for scalability issues in photonics quantum technologies.