Recoil frequency measurement with ppb-level uncertainty by 6Li atom interferometer

We report a first realization of cold atom interferometers with the lightest alkali metal 6Li atoms and precisely measure the recoil frequency. The atoms are cooled to approach the half of the photon-recoil limit by using a narrow 2S -> 3P ultraviolet transition. A magic magnetically insensitive state, a high-efficiency state preparation, and a frequency-insensitive Raman coupling are developed to overcome the challenges from the half-integer spin and hyperfine interaction of atoms. A conjugated Ramsey-Borde ' interferometer with crossed Raman beams is realized with a coherence time longer than 2.3 ms. The four sets of interferometers developed using geometric relations greatly eliminate the error from the angle between Raman beams. The measured recoil frequency is omega r = 2 pi x 73 672.789 (36) Hz, representing the most precise measurement of the recoil frequency of 6Li by using the atom interferometer so far. The realized 6Li cold atom interferometer is not only an effective supplement to the existing interferometers, but also provides a good candidate in precision measurement owing to its low mass and high recoil frequency.

Automated summary

We report the first realization of cold atom interferometers using 6Li, the lightest alkali metal, and measure the recoil frequency with great precision. By cooling the atoms using a narrow 2S -> 3P ultraviolet transition, we approach half of the photon-recoil limit. We overcome the challenges of half-integer spin and hyperfine interaction by developing a magnetically insensitive state, a high-efficiency state preparation, and a frequency-insensitive Raman coupling. A Conjugated Ramsey-Borde interferometer with crossed Raman beams is realized, and the measured recoil frequency represents the most precise measurement so far using an atom interferometer.