  Coherent exchange of single photons is at the heart of applied Quantum
Optics. The negatively-charged silicon vacancy center in diamond is among most
promising sources for coherent single photons. Its large Debye-Waller factor,
short lifetime and extraordinary spectral stability is unique in the field of
solid-state single photon sources. However, the excitation and detection of
individual centers requires high numerical aperture optics which, combined with
the need for cryogenic temperatures, puts technical overhead on experimental
realizations. Here, we investigate a hybrid quantum photonics platform based on
silicon-vacancy center in nanodiamonds and metallic bullseye antenna to realize
a coherent single-photon interface that operates efficiently down to low
numerical aperture optics with an inherent resistance to misalignment.
