Coupling 1D Atom Arrays to an Optical Nanofiber: Platform for Waveguide QED experiments

The coupling of cold atoms to 1D nanoscale waveguides have opened new avenues of research. The waveguide in our case is a nanofiber, which confines light transversally to a subwavelength scale. The guided light exhibits a strong evanescent field allowing enhanced atom-photon interaction in the vicinity of nanofiber. In our experiment, a cold atomic cloud is first interfaced with an optical nanofiber. By using an optical lattice in the evanescent field, the atoms are then trapped in 1D atomic arrays close to the nanofiber. In this platform, I will report on two experiments. First, the creation of heralded collective excitation in the atomic ensemble and its subsequent conversion into a single photon with high efficiency. Second, the observation of Bragg reflection, as high as 75%, from 2000 trapped atoms when the period of the lattice is made close to commensurate with the resonant wavelength. The reflection shows dependency on orientation of the probe polarization relative to the atomic arrays - a chiral signature in nanoscale waveguide-QED systems. The ability to control photon transport in 1D waveguides coupled to spin systems would enable novel quantum networking capabilities and the study of many-body effects arising from long-range 
interactions.