  We demonstrate an efficient optical guiding technique for coupling cold atoms
in the near field of a planar nanophotonic circuit, and realize large
atom-photon coupling to a whispering-gallery mode in a microring resonator with
a single-atom cooperativity $C\gtrsim 8$. The guiding potential is created by
diffracted light on a nanophotonic waveguide that smoothly connects to a dipole
trap in the far field for atom guiding with subwavelength precision. We observe
atom-induced transparency for light coupled to a microring, characterize the
atom-photon coupling rate, extract guided atom flux, and demonstrate on-chip
photon routing by single atoms. Our demonstration promises new applications
with cold atoms on a nanophotonic circuit for chiral quantum optics and quantum
technologies.
