We propose highly efficient hybrid plasmonic bullseye antennas for collecting photon emission from nm-sized quantum emitters. In our approach, the emitter radiation is coupled to surface plasmon polaritons that are consequently converted into highly directional out-of-plane emission. The proposed configuration consists of a high-index titania bullseye grating separated from a planar silver film by a thin low-index silica spacer layer. Such hybrid systems are theoretically capable of directing 85% of the dipole emission into a 0.9 NA objective, while featuring a spectrally narrow-band tunable decay rate enhancement of close to 20 at the design wavelength. Hybrid antenna structures were fabricated by standard electron-beam lithography without the use of lossy adhesion layers that might be detrimental to antenna performance. The fabricated antennas remained undamaged at saturation laser powers exhibiting stable operation.For experimental characterization of the antenna properties, a fluorescent nanodiamond containing multiple nitrogen vacancy centers (NV-center) was deterministically 1 arXiv:1804.04433v1 [physics.optics] 12 Apr 2018 placed in the bullseye center, using an atomic force microscope. Probing the NV-center fluorescence we demonstrate resonantly enhanced, highly directional emission at the design wavelength of 670 nm, whose characteristics are in excellent agreement with our numerical simulations.Efficient collection of photons from single quantum emitters (QE) is a key requirement for many quantum technological applications, 1 utilizing on-demand photon generation, optical spin read-out 2,3 or coalescence of indistinguishable photons. 4,5 The efficiency by which photons can be collected is, however, often compromised by the non-unity quantum yield and relatively omnidirectional emission pattern of typical QEs, whether it is a molecule, quantum dot or solid state defect. 6 Fortunately, both aspects can be improved upon by engineering the photonic enviroment. Quantum yield may be increased by accelerating the radiative spontaneous decay rate, relative to intrinsic nonradiative decay, via the Purcell effect. 7 Directional emission is typically achieved by two approaches; 8 either a geometricalor a mode-coupling approach. The geometrical approach relies on redirecting far-field emission by reflection or refraction on appropriately shaped surfaces, such as a parabolic mirror 9 or solid immersion lens. 10 Alternatively, the mode-coupling approach is based on near-field coupling QE emission to an antenna or waveguide mode. The emission pattern then conforms to that of the antenna, 11 while for detection with an objective, plane film waveguide modes may be redirected to free space by leakage into high index substrates 12 or scattering on periodic gratings. 13,14 For highly directional emission, the circular symmetric bullseye grating is particularly attractive as tight beaming of photons is achievable by appropriate