A nanophotonic atom trap toward collective atom-light interactions and the design of a novel protection layer for superconducting circuits toward a hybrid quantum system

A centimeter long silicon nitride nanophotonic waveguide with inverse-tapered ends has been developed to address and trap many cold neutral atoms ($^{87}$Rb) for studying collective atom-light interactions and a hybrid quantum system. Two-color evanescent trapping fields (750nm and 1064nm) of guided modes (TE0) can confine cold neutral atoms above the waveguide, and its inverse-tapered waveguide-end has been used for higher input coupling. For a hybrid quantum system which couples trapped cold neutral atoms to superconducting (SC) circuits through magnetic dipole coupling, we consider a novel SC protection layer because SC circuits are vulnerable to the scattered light from trapping fields. Therefore, we design several types of dielectric and lossy multi-wavelength Bragg layers to protect SC circuits from NIR scattered optical photons and from a broadband MIR blackbody radiation of the nanophotonic device, considering the maximal back-transmission of the SC circuits' electro-magnetic fields through the layer and the heat transfer to SC circuits through the protection layer from absorbed scattered photons.