Cold-atom clock based on a diffractive optic

Abstract

Clocks based on cold atoms offer unbeatable accuracy and long-term stability, but their use in portable quantum technologies is hampered by a large physical footprint. Here, we use the compact optical layout of a grating magneto-optical trap (gMOT) for a precise frequency reference. The gMOT collects $10^7$ ${}^{87}$Rb atoms, which are subsequently cooled to $20\hat{I}¼$K in optical molasses. We optically probe the microwave atomic ground-state splitting using lin$\perp$lin polarised coherent population trapping and a Raman-Ramsey sequence. With ballistic drop distances of only $0.5$mm, the measured short-term fractional frequency stability is $2\times 10^{-11}/\sqrt{\ddot{I}}„$.

8 pages, 4 figures