Efficient fiber in-line single photon source based on colloidal single quantum dots on an optical nanofiber

We demonstrate a fiber in-line single photon source based on a hybrid system of colloidal single quantum dots deposited on an optical nanofiber and cooled down to cryogenic temperature (3.7 K). We show that a charged state (trion) of the single quantum dot exhibits a photo-stable emission of single photons with high quantum efficiency, narrow linewidth (3 meV FWHM) and fast decay time ($10.0\pm 0.5$ ns). The single photons are efficiently coupled to the guided modes of the nanofiber and eventually to a single mode optical fiber. The brightness (efficiency) of the single photon source is estimated to be $16\pm 2\mathrm{\%}$ with a maximum photon count rate of $1.6\pm 0.2$ MHz and a high single photon purity ($g^2(0)=0.11\pm 0.02$). The device can be easily integrated to the fiber networks paving the way for potential applications in quantum networks.