Quantum simulation beyond mean field

A simulator with direct access to the wave field

Quantum simulation with light combines programmable initial conditions, tunable interactions and spatially resolved detection. In our platform, propagation implements the evolution of a many-body Hamiltonian while interferometry gives access to both quadratures of the field. The challenge is to move beyond the mean density and identify the fluctuations and correlations that certify the underlying quantum process.

Quantum noise created by a quench

When interactions are switched on at the entrance of the vapour cell, the incoming optical vacuum is no longer the ground state of the interacting fluid. Opposite-momentum Bogoliubov excitations are then created in correlated pairs. Mathematically, this transformation is the same as two-mode squeezing. The second quench at the cell exit mixes the modes once more and produces an interference pattern analogous to Sakharov oscillations.

We develop complementary measurements of these correlations, from spatially resolved intensity fluctuations to mode-selective quadrature detection and covariance reconstruction. Their common purpose is to separate spontaneous quantum noise from stimulated and technical backgrounds.

Simulating geometry and collective matter

Collective excitations propagate in an effective spacetime defined by the fluid’s density and velocity. Engineering these quantities lets us investigate particle creation in expanding backgrounds, curved-spacetime dynamics and the fate of symmetry-breaking modes outside equilibrium. These experiments turn analogue gravity into a measurable many-body problem rather than a purely kinematic analogy.

Towards a supersolid of light

We are exploring regimes in which effective attraction and nonlocal response favour a stable, periodically modulated fluid. Such a state is a candidate supersolid only if it combines crystalline density order with long-range phase coherence. Our programme therefore tests both properties and searches for the two collective Goldstone branches expected when translational and phase symmetries are broken together.

This work extends the photonic simulator from weakly perturbed superfluids to new phases of correlated light. The same correlation and cumulant measurements used for quenches and turbulence provide the stringent diagnostics needed to distinguish a genuine many-body phase from a classical intensity pattern.

Associated publications