Cold-atom clock based on a diffractive optic

Elvin, R. and Hoth, G. W. and Wright, M. and Lewis, B. and McGilligan, J. P. and Arnold, A. S. and Griffin, P. F. and Riis, E. (2019) Cold-atom clock based on a diffractive optic. Optics Express, 27 (26). pp. 38359-38366. ISSN 1094-4087 (

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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 87Rb atoms, which are subsequently cooled to 20 µK in optical molasses. We optically probe the microwave atomic ground-state splitting using lin┴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 × 10 −11/√τ.