Mainz 2026 – scientific programme

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A: Fachverband Atomphysik

A 2: Ultra-cold Plasmas and Rydberg Systems I (joint session A/Q)

A 2.1: Invited Talk

Monday, March 2, 2026, 11:45–12:15, N 1

Experimental investigation of strongly interacting quantum fluids of light in rydberg atoms — •Amar Bellahsene, Tom Bienaimé, and Shannon Whitlock — Université de Strasbourg, CESQ-ISIS, Strasbourg, France

Photons are ideal quantum systems - easy to generate, manipulate, and detect - but their absence of mutual interactions limits their use for many-body physics and quantum simulation. A powerful approach to engineer strong and tunable photon-photon interactions is to propagate light through an ultracold atomic gas coupled to Rydberg states under electromagnetically induced transparency (EIT). This medium provides strong light-matter coupling and collectively enhanced nonlinearities, allowing photons to acquire an effective mass and interact, forming a platform for quantum fluids of light. My PhD work explores this regime using ultracold potassium 39 atoms in a Magneto-optical trap. We characterize how atomic nonlinear media mediate interactions between photons by measuring the Kerr nonlinearity in a two-level system and comparing it to the large enhancement achieved in a three-level Rydberg-EIT configuration. The nonlinear phase shifts are extracted with a Mach-Zehnder interferometer, providing a sensitive probe of interaction-induced optical response. By combining spatial structuring of the light field, strong Rydberg interactions, and interferometric detection, the goal is to demonstrate a quantum nonlinear medium where photons behave as interacting quasiparticles - opening the way toward the realization of a quantum fluid of light.

Keywords: Optical Kerr nonlinearities; Rydberg electromagnetically induced transparency; Quantum fluid of light; Cooperativity; Photon-photon interactions