A novel experimental platform for waveguide QED with cold atoms and photonic crystal waveguides

Novel platforms interfacing trapped cold atoms and guided light in nanoscale waveguides are a promising route to achieve a regime of strong coupling between light and atoms in single pass.

In this endeavour, photonic crystals offer two main assets: slow light, which can enhance the atom-photon interaction, and band gaps, which can be used to form atom-photon bound states which can be resources for quantum simulation or variational quantum computing. However, implementing these waveguide QED platforms is challenging as they should combine facilitated optical access for atom transport and trapping via guided modes. In this presentation, I will emphasize a proposal and experimental first steps to interface Rb atoms with a photonic crystal waveguide based on a large-index GaInP slab. Using a specifically tailored half-W1 design, with a strong emphasis on robustness to nanofabrication imperfections, we show that a large coupling to the waveguide can be obtained and that guided modes can be used to form two-color dipole traps for atoms at about 100 nm from the edge of the structure. This very realistic (and fabricated) optimized device should greatly improve the level of experimental control and facilitate the atom integration. We might finally benefit from the optical tweezer toolbox to get the atoms in the traps. As such, Laguerre-Gauss tweezers are promising as they could allow for tighter traps and reduce reflections on the waveguide surface.