Mainz 2026 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 16: Ultracold Matter IV – Bosons, Rydberg Systems, and Others (joint session Q/A)

A 16.3: Vortrag

Mittwoch, 4. März 2026, 15:00–15:15, P 2

Dissipative Optical Nonlinearities in Ultracold Ytterbium — •Tangi Legrand, Xin Wang, Anthea Nitsch, Chris George, Wolfgang Alt, Eduardo Uruñuela, and Sebastian Hofferberth — Institute of Applied Physics, University of Bonn, Germany

Photon-photon interactions at the single-quantum level can be achieved and controlled by strong optical nonlinearities arising from interactions between Rydberg excitations in dense and ultracold atomic ensembles. Two-valence-electron species such as ytterbium offer novel advantages, including narrow-linewidth laser-cooling, optical detection and ionization, and access to long-lived nuclear-spin memory states.

In this talk, we present an experiment that investigates the interactions between a large number of Rydberg polaritons propagating simultaneously through a high-density ¹⁷⁴Yb medium. Using a narrow-line magneto-optical trap, we prepare dense clouds at microkelvin temperatures and drive Rydberg transitions via a counter-propagating two-photon scheme. A flat-top excitation beam, together with the long Rayleigh range of the near-UV probe, result in a high optical depth per blockade volume. We then generate and characterize Rydberg polaritons under electromagnetically induced transparency conditions and investigate how ytterbium’s atomic structure–such as the absence of hyperfine splitting in bosonic isotopes–modifies dephasing mechanisms, blockade behavior, and collective dynamics. In particular, we detect dissipative nonlinearities through photon-antibunching and assess the coherence of the stored excitation.

Keywords: Nonlinear Quantum Optics; Ytterbium; Rydberg Atoms; Polaritons