High Efficiency RF Antennas for Quantum Sensing Applications

Radio frequency (RF) signals are frequently used in emerging quantum applications due to their spin state manipulation capability. Efficient coupling of RF signals into a particular quantum system requires the utilization of carefully designed and fabricated antennas. Nitrogen vacancy (NV) defects in diamond are commonly utilized platforms in quantum sensing experiments with the optically detected magnetic resonance (ODMR) method, where an RF antenna is an essential element. We report on the design, fabrication, and optimization principles of coplanar RF antennas for quantum sensing applications. Novel coplanar waveguide RF antennas were designed and fabricated with over 30 dB experimental return loss at 2.87 GHz, the zero-field splitting (ZFS) frequency of the negatively charged NV defect in diamond. The efficiencies of the antenna were demonstrated in magnetic field quantum sensing experiments with NV color centers in diamond. An RF amplifier was not needed and the 0dB (1 milliwatt) output of a standard RF generator was adequate to run the ODMR experiments due to high efficiency of the novel RF antennas.