CHARNAY Elias : Generalised hydrodynamics of optical soliton gases

Résumé de thèse :

Generalised Hydrodynamics brought with success a new macroscopic description of thermodynamics and hydrodynamics in integrable systems. One of its strenghts is the hydrodynamical expansion, allowing a description of weak integrability breaking such as traps or exterior forces. As such, it became subject to active research in cold atoms and in quantum N-body dynamics. It also predicts large-scale correlations.

We can compute these space-time correlations for the infinitely many conserved quantities in integrable equations. In particular, for the Non-Linear Schrödinger Equation, it is possible to compute exactly the intensity correlation associated to the mass. It takes a ballistic form, with a polynomial decrease, which comes from the fact that solitons are quasi-particles and propagate with a constant effective velocity only modified by interactions.

We propose here experiments in a recirculating fibre loop allowing measurements of these intensity correlations. Our system allows the generation of arbritrary initial condition in intensity and phase, and its propagation with few losses. At each roundtrip, the signal propagates in 5km of standard single-mode optical fibre where losses are compensated by a Raman laser. We extract 10% of the circulating light to measure intensity and reconstruct the space-time dynamics. From this, we compute the correlations and show that they follow a polynomial law, proving ballistic transport and validating Generalised Hydrodynamics in this system.

Doctorant : CHARNAY Elias

Directeur de thèse : SURET Pierre, COPIE François