Manipulation of single nanodiamonds to ultrathin fiber-taper nanofibers and control of NV-spin states toward fiber-integrated λ-systems

We report on the coupling of single nitrogen vacancy (NV) centers to ultrathin fiber-taper nanofibers by the manipulation of single diamond nanocrystals on the nanofibers under real-time observation of nanodiamond fluorescence. Spin-dependent fluorescence of the single NV centers is efficiently detected through the nanofiber. We show control of the spin sub-level structure of the electronic ground state using an external magnetic field and clearly observe a frequency fine tuning of m(S) = vertical bar +/- 1 >. This observation demonstrates a possibility of realizing fiber-integrated quantum lambda-systems, which can be used for various quantum information devices including push-pull quantum memory and quantum gates.