MISTiQ-Light — Mott Insulator Transition in a Quantum Fluid of Light

MISTiQ-Light is an ERC Consolidator Grant led by Quentin Glorieux at the Laboratoire Kastler Brossel. Running from October 2023 to September 2028, the project aims to push paraxial fluids of light beyond the mean-field regime and observe a superfluid-to-Mott-insulator transition for photons.

From a laser beam to quantum matter

In a nonlinear medium, the paraxial propagation of light follows an equation closely related to the Gross–Pitaevskii equation for a quantum gas. Diffraction gives photons an effective mass, while the optical nonlinearity produces effective photon–photon interactions. MISTiQ-Light combines this mapping with a dense, laser-cooled rubidium cloud to reach interaction strengths at which genuinely quantum many-body effects become measurable.

Scientific objectives

The project is organised around four challenges:

  1. Build a strongly nonlinear cold-atom platform. Atomic coherences are used to enhance and independently control the linear and nonlinear optical response experienced by the fluid.
  2. Engineer a photonic Bose–Hubbard model. A programmable optical lattice sets the tunnelling energy, while photon–photon interactions provide the on-site interaction.
  3. Measure physics beyond mean field. Photon-resolved imaging and spatially resolved homodyne detection will probe fluctuations, correlations, quantum depletion and entanglement.
  4. Cross the superfluid–Mott transition. The central goal is a photonic state with a well-defined number of photons on each lattice site and suppressed number fluctuations.

Why it matters

For fundamental physics, the experiment would provide a new platform for studying strongly correlated, driven and out-of-equilibrium quantum matter with direct optical access to amplitude, phase and correlations.

For quantum technologies, a photonic Mott state could act as a large parallel source of controlled photon-number states. Unlike material particles in an optical lattice, the photons can leave the simulator and be routed towards photonic circuits, detectors or communication channels.

Project information

See the MISTiQ-Light entry in Sorbonne Université’s ERC project portfolio.