Experimental realization of an optical antenna for collecting 99% of photons from a quantum emitter

We present the fabrication and characterization of an optical antenna that converts the dipolar radiation of a quantum emitter to a directional beam with 99% efficiency. Aside from its implications for efficient detection of nanoscopic emitters, this antenna facilitates a deterministic single-photon source with applications in quantum information processing, metrology and sub-shot-noise detection of absorption. We discuss the photophysical limitations of the currently used quantum emitters for the realization of such a device.