Precision timing is essential in the GPS navigation system, for financial markets and for fundamental science. The ultimate timekeepers are atoms, as microwave and optical transitions within a collection of isolated and most importantly identical single atoms form the ultimate accurate and precise frequency reference. Atomic clocks using the same atoms cooled down 108 times lower than room temperature atoms can yield 104 times better sensitivity simply because they are 104 times slower and we can measure their transitions correspondingly longer.

Our cold atom clock experiments are aided by our expertise in grating magneto-optical traps (GMOTs). The general principle is illustrated below, and highlighted in these news items: Nature Nanotech paper, May 2013 cover + News and ViewsStrathclyde News. The GMOT arose as a planar geometry extension of our shadow-free 4-beam pyramidal magneto-optical trap. Diffraction gratings are used to split and steer a single incoming beam into e.g. a tripod of diffracted beams, allowing trapping in the four-beam overlap volume. Using the technique with our micro-fabricated gratings we trap and subsequently sub-Doppler cool 87Rb atoms to a recent record of 3μK. Our latest paper on the use of GMOTs for an atomic clock, is available here.

This work is part of the continuing UK Quantum Technology Hub in Sensing and Metrology.


Funding: EPSRC grants EP/M013294/1 and EP/T001046/1, ESA 4000110231/13/NL/PA, DSTL DSTLX-100095636R, InnovateUK EP/M50824X/1.


  • B. Lewis, R. Elvin, A. S. Arnold, E. Riis, and P. F. Griffin, A grating-chip atomic fountain, Appl. Phys. Lett. 121, 164001 (2022).
  • S. Dyer, P. F. Griffin, A. S. Arnold, F. Mirando, D. P. Burt, E. Riis, and J. P. McGilligan, Micro-machined deep silicon atomic vapor cells, J. Appl. Phys. 132, 134401 (2022).
  • J.P. McGilligan, K. Gallacher, P.F. Griffin, D.J. Paul, A.S. Arnold, and E. Riis, Micro-fabricated components for cold atom sensors, Rev. Sci. Instrum. 93, 091101 (2022).
  • A. Bregazzi, P.F. Griffin, A.S. Arnold, D.P. Burt, G. Martinez, R. Boudot, J. Kitching, E. Riis & J.P. McGilligan, A simple imaging solution for chip-scale laser cooling, Appl. Phys. Lett. 119, 184002 (2021).
  • O.S. Burrow, P.F. Osborn, E. Boughton, F. Mirando, D.P. Burt, P.F. Griffin, A.S. Arnold, and E. Riis, Stand-alone vacuum cell for compact ultracold quantum technologiesAppl. Phys. Lett. 119, 124002 (2021).
  • R. Elvin, M.W. Wright, B. Lewis, B.L. Keliehor, A. Bregazzi, J.P. McGilligan, A.S. Arnold, P.F. Griffin, and E. Riis, Towards a compact, optically interrogated, cold-atom microwave clockAdv. Opt. Tech. 9, 297 (2020).
  • J.P. McGilligan, K.R. Moore, A. Dellis, G.D. Martinez, E. de Clercq, P.F. Griffin, A.S. Arnold, E. Riis, R. Boudot & J. Kitching, Laser cooling in a chip-scale platformAppl. Phys. Lett. 117, 054001 (2020).
  • R. Elvin, G.W. Hoth, M. Wright, B. Lewis, J.P. McGilligan, A.S. Arnold, P. F. Griffin & E. Riis, Cold-atom clock based on a diffractive opticOpt. Express 27, 38359 (2019).
  • G. W. Hoth, R. Elvin, M. Wright, B. Lewis, A. S. Arnold, P. F. Griffin & E. Riis, Towards a compact atomic clock based on coherent population trapping and the grating magneto-optical trapProceedings of SPIE 10934, 109342E (2019).
  • R. Elvin, G.W. Hoth, M.W. Wright, J.P. McGilligan, A.S. Arnold, P.F. Griffin & E. Riis, Raman-Ramsey CPT with a grating magneto-optical trap, IEEE EFTF (2018).
  • J.P. McGilligan, P.F. Griffin, R. Elvin, S.J. Ingleby, E. Riis & A.S. Arnold, Grating chips for quantum technologies, Sci. Rep. 7, 384 (2017).
  • J.P. McGilligan, R. Elvin, P.F. Griffin, E. Riis & A.S. Arnold, Utilising diffractive optics towards a compact, cold atom clock, IEEE EFTF (2016).
  • J.P. McGilligan, P.F. Griffin, E. Riis & A.S. Arnold, Diffraction-grating characterization for cold-atom experiments, JOSAB 33, 1271 (2016).
  • J.P. Cotter, J.P. McGilligan, P.F. Griffin, I.M. Rabey, K. Docherty, E. Riis, A.S. Arnold & E.A. Hinds, Design and fabrication of diffractive atom chips for laser cooling and trapping, Appl. Phys. B 122 (2016).
  • J.P. McGilligan, P.F. Griffin, E. Riis & A.S. Arnold, Phase-space properties of magneto-optical traps utilising micro-fabricated gratingsOpt. Express 23, 8948 (2015).
  • C.C. Nshii, M. Vangeleyn, J.P. Cotter, P.F. Griffin, E.A. Hinds, C.N. Ironside, P. See, A.G. Sinclair, E. Riis & A.S. Arnold, A surface-patterned chip as a strong source of ultracold atoms for quantum technologiesNature Nanotech. 8, 321 (2013).
  • M. Vangeleyn, P.F. Griffin, E. Riis & A.S. Arnold, Laser cooling with a single laser beam and a planar diffractorOpt. Lett. 35, 3453 (2010).
  • M. Vangeleyn, P.F. Griffin, E. Riis & A.S. Arnold, Single-laser, one beam, tetrahedral magneto-optical trap, Opt. Express 17, 13601 (2009).