  We propose a field-based design for dielectric antennas to interface diamond
color centers with a Gaussian propagating far field. This antenna design
enables an efficient spin-photon interface with a Purcell factor exceeding 400
and a 93% mode overlap to a 0.4 numerical aperture far-field Gaussian mode. The
antenna design is robust to fabrication imperfections, such as variations in
the dimensions of the dielectric perturbations and the emitter dipole location.
The field-based dielectric antenna design provides an efficient free-space
interface to closely packed arrays of quantum memories for multiplexed quantum
repeaters, arrayed quantum sensors, and modular quantum computers.
