  Diamond's nitrogen vacancy (NV) center is an optically active defect with
long spin coherence times, showing great potential for both efficient nanoscale
magnetometry and quantum information processing schemes. Recently, both the
formation of buried 3D optical waveguides and high quality single NVs in
diamond were demonstrated using the versatile femtosecond laser-writing
technique. However, until now, combining these technologies has been an
outstanding challenge. In this work, we fabricate laser written photonic
waveguides in quantum grade diamond which are aligned to within micron
resolution to single laser-written NVs, enabling an integrated platform
providing deterministically positioned waveguide-coupled NVs. This fabrication
technology opens the way towards on-chip optical routing of single photons
between NVs and optically integrated spin-based sensing.
