Towards a compact, optically-interrogated, cold-atom microwave clock

Elvin, Rachel and Wright, Michael W. and Lewis, Ben and Keliehor, Brendan L. and Bregazzi, Alan and McGilligan, James P. and Arnold, Aidan S. and Griffin, Paul F. and Riis, Erling (2020) Towards a compact, optically-interrogated, cold-atom microwave clock. Advanced Optical Technologies, 9 (5). pp. 297-303. ISSN 2192-8584 (

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A compact platform for cold atoms opens a range of exciting possibilities for portable, robust, and accessible quantum sensors. In this work we report on the development of a cold-atom microwave clock in a small package. Our work utilises the grating magneto-optical trap and high-contrast coherent population trapping in the lin⊥lin polarisation scheme. We optically probe the atomic round-state splitting of cold 87Rb atoms using a Ramsey-like sequence whilst the atoms are in free-fall. We have measured a short-term fractional frequency stability of 5×10−11/√t with a projected quantum projection noise limit at the 10 −13/√t level.