Experimental two-dimensional Raman cooling with orthogonal geometry

Despite the remarkable achievements in precision measurement, the transverse diffusion of atom ensembles remains the main factor that hinders further improvements in the accuracy of matter-wave interferometry. This paper demonstrates a two-dimensional deep cooling method based on the orthogonal Raman geometry. After 35 milliseconds of cooling, the atom ensemble reaches a temperature lower than 100 nanokelvins in the horizontal plane, and a cooling efficiency of 30% approximately. In the meantime, the cooled atoms exhibit high uniformity in all directions. These characteristics render this cooling protocol more suitable for quantum sensing compared with ultracold atoms or optical molasses.