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

Abstract

We report a first realization of cold atom interferometers with the lightest alkali metal ^{6}Li 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[over ́] 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 ω_{r}=2π×73672.789(36) Hz, representing the most precise measurement of the recoil frequency of ^{6}Li by using the atom interferometer so far. The realized ^{6}Li 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.