Combining Cold Atoms and Photonic Crystal Waveguides for Strong Interaction in Single Pass – NanoStrong

The NanoStrong project aims at the integration of atomic physics and photonic-crystal slow-mode waveguides to develop an original single-pass platform where strong interactions between guided light and cold atoms can be engineered. This approach holds the promise of new capabilities due to the unique combination of tight transverse confinement of the light, enhanced interaction via the engineering of the density of states and possible complex structuration of the circuit. This line of research will eventually provide better figures of merit and scalability than in free-space implementations but also tailored functionalities not achievable in current physical interfaces, including single-photon addressing of collective atomic excitations without the need of a cavity. These functionalities offer unique applications to integrated quantum technologies, quantum non-linear optics and state engineering.


Based upon a promising material (GaInP) mastered by one of the teams and the unique expertise of the consortium in structure design, the project will target the realization of a slow-mode photonic-crystal waveguide coupled with an ensemble of cold atoms trapped above the membrane via the evanescent fields. This original realization would provide a novel platform where individual atoms in an ensemble can strongly interact with single photons via an enhanced interaction probability, in a single-pass configuration, in contrast to cavity-QED schemes.


More specifically, the new research activities that we propose to undertake are as follows:


-The design and fabrication of slow-mode photonic-crystal waveguides compatible with alkaline atoms.
-The laboratory implementation of atomic ensembles trapped in the vicinity of the structure.
-The demonstration of efficient coupling between the trapped atoms and the structure modes.
-The realization of a single-photon switch by state-dependent conditional reflection.


To reach these objectives, the NanoStrong project brings together 3 academic partners with internationally recognized expertise. They gather the required complementary knowledge and techniques in quantum optics, atomic physics, nanophotonics design and fabrication. Due to the nature of the project, which includes design, fabrication, and protocol implementations, the partners will naturally work in very close collaboration. The project will finally deliver an enabling toolbox combining atomic physics, quantum optics and nanophotonics. This unique toolbox will provide an original playground for strong photon-photon interactions.