Skip to content
Licensed Unlicensed Requires Authentication Published by De Gruyter September 7, 2019

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

  • Rachel Elvin EMAIL logo , Michael W. Wright , Ben Lewis , Brendan L. Keliehor , Alan Bregazzi , James P. McGilligan , Aidan S. Arnold , Paul F. Griffin and Erling Riis


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 linlin polarisation scheme. We optically probe the atomic ground-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 5×1011/τ with a projected quantum projection noise limit at the 1013/τ level.

Corresponding author: Rachel Elvin, SUPA, University of Strathclyde, G4 0NG Glasgow, UK,

Award Identifier / Grant number: EP/M013294/1

Award Identifier / Grant number: EP/T001046/1

Award Identifier / Grant number: DSTLX1000138605


The authors gratefully thank Dr. Greg Hoth for his excellent work and support in driving the project.

  1. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  2. Research funding: The authors acknowledge financial support from EPSRC through the UK Quantum Technology Hub for Sensors and Metrology/Timing (EP/M013294/1, EP/T001046/1) and from the Defence Science and Technology Laboratory (DSTLX1000138605). The data supporting this publication can be accessed at:

  3. Competing interests: Authors state no conflict of interest.


[1] A. D. Ludlow, M. M. Boyd, J. Ye, E. Peik, and P. Schmidt, “Optical atomic clocks,” Rev Mod Phys, vol. 87, p. 637, 2015. in Google Scholar

[2] N. Huntemann, C. Sanner, B. Lipphardt, C. Tamm, and E. Peik, “Single-ion atomic clock with 3 × 10−18 systematic uncertainty,” Phys Rev Lett, vol. 116, 2016, Art no. 063001. in Google Scholar

[3] S. L. Campbell, R. B. Hutson, G. E. Marti, et al., “A Fermi-degenerate three-dimensional optical lattice clock,” Science, vol. 358, p. 90, 2017. in Google Scholar

[4] S. M. Brewer, J. S. Chen, A. M. Hankin, et al., “Al + 27 quantum-logic clock with a systematic uncertainty below 10−18,” Phys Rev Lett, vol. 123, 2019, Art no. 033201. in Google Scholar

[5] S. B. Koller, J. Grotti, S. Vogt, et al., “Transportable optical lattice clock with 7 × 10−17 uncertainty,” Phys Rev Lett, vol. 118, 2017, Art no. 073601. in Google Scholar

[6] J. Grotti, S. Koller, S. Vogt, et al., “Geodesy and metrology with a transportable optical clock,” Nat Phys, vol. 14, p. 437, 2018. in Google Scholar

[7] MuQuans MuClock. Available at: [accessed: May 27, 2020].Search in Google Scholar

[8] Spectradynamics cRb-Clock. Available at: [accessed: May 27, 2020].Search in Google Scholar

[9] B. Pelle, B. Desruelle, R. Szmuk, and D. Holleville, “Cold-atom-based commercial microwave clock at the 10–15 level,” in 2017 Joint Conf. of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS), 2017. (IEEE, Besancon) in Google Scholar

[10] R. J. Hendricks, F. Ozimek, K. Szymaniec, et al., “Cs fountain clocks for commercial realizations—an improved and robust design,” in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, vol. 66, p. 624, 2018.10.1109/TUFFC.2018.2874550Search in Google Scholar PubMed

[11] F. G. Ascarrunz, Y. O. Dudin, M. C. Delgado Aramburo, et al., “A portable cold 87Rb atomic clock with frequency instability at one day in the 10–15 range,” in 2018 IEEE International Frequency Control Symposium (IFCS), 2018. (IEEE, Olympic Valley, CA.) in Google Scholar

[12] C. C. Nshii, M. Vangeleyn, J. P. Cotter, et al., “A surface-patterned chip as a strong source of ultracold atoms for quantum technologies,” Nat Nanotechnol, vol. 8, p. 321, 2013. in Google Scholar

[13] J. P. McGilligan, P. F. Griffin, R. Elvin, S. J. Ingleby, E. Riis, and A. S. Arnold, “Grating chips for quantum technologies,” Sci Rep, vol. 7, p. 384, 2017. in Google Scholar

[14] G. W. Hoth, B. Pelle, S. Riedl, J. Kitching, and E. A. Donley, “Point source atom interferometry with a cloud of finite size,”Appl Phys Lett, vol. 109, 2016, Art no. 071113. in Google Scholar

[15] X.-H. Bao, A. Reingruber, P. Dietrich, et al., “Efficient and long-lived quantum memory with cold atoms inside a ring cavity,” Nat Phys, vol. 8, p. 517, 2012. in Google Scholar

[16] Kelvin Nanotechnology gMOT. Available at: [accessed: May 27, 2020].Search in Google Scholar

[17] R. Elvin, G. W. Hoth, M. Wright, et al., “Cold-atom clock based on a diffractive optic,” Opt Express, vol. 27, p. 38359, 2019. in Google Scholar

[18] G. W. Hoth, R. Elvin, M. Wright, et al., “Towards a compact atomic clock based on coherent population trapping and the grating magneto-optical trap,” in Proc. SPIE 10934, Optical, Opto-Atomic, and Entanglement-Enhanced Precision Metrology, 2019. (SPIE, San Francisco) in Google Scholar

[19] J. Vanier, “Atomic clocks based on coherent population trapping: a review,” Appl Phys B, vol. 81, p. 421, 2005. in Google Scholar

[20] S. Knappe, V. Shah, P. D. D. Schwindt, et al., “A microfabricated atomic clock,” Appl Phys Lett, vol. 85, p. 1460, 2004. in Google Scholar

[21] A. V. Taichenachev, V. I. Yudin, V. L. Velichansky, and S. A. Zibrov, “On the unique possibility of significantly increasing the contrast of dark resonances on the D1 line of 87Rb,” JETP Lett, vol. 82, p. 398, 2005. in Google Scholar

[22] E. Blanshan, S. M. Rochester, E. A. Donley, and J. Kitching, “Light shifts in a pulsed cold-atom coherent-population-trapping clock,” Phys Rev A, vol. 91, 2015, Art no. 041401. in Google Scholar

[23] F. X. Esnault, E. Blanshan, E. N. Ivanov, R. E. Scholten, J. Kitching, and E. A. Donley, “Cold-atom double-Λcoherent population trapping clock,” Phys Rev A, vol. 88, 2013, Art no. 042120. in Google Scholar

[24] T. Zanon, S. Guerandel, E. de Clercq, D. Holleville, N. Dimarcq, and A. Clairon, “High contrast Ramsey fringes with coherent-population-trapping pulses in a double lambda atomic system,” Phys Rev Lett, vol. 94, p. 193002, 2005. in Google Scholar

[25] C. Xi, Y. Guo-Qing, W. Jin, and Z. Ming-Sheng, “Coherent population trapping-ramsey interference in cold atoms,” Chin Phys Lett, vol. 27, p. 113201, 2010. in Google Scholar

[26] M. Abdel Hafiz, G. Coget, P. Yun, S. Guérandel, E. de Clercq, and R. Boudot, “A high-performance Raman-Ramsey Cs vapor cell atomic clock,” J Appl Phys, vol. 121, p. 104903, 2017. in Google Scholar

[27] S. V. Kargapoltsev, J. Kitching, L. Hollberg, A. V. Taichenachev, V. L. Velichansky, and V. I. Yudin, “High-contrast dark resonance in σ+ − σ−optical field,” Laser Phys Lett, vol. 1, p. 495, 2004. in Google Scholar

[28] X. Liu, V. I. Yudin, A. V. Taichenachev, J. Kitching, and E. A. Donley, “High contrast dark resonances in a cold-atom clock probed with counterpropagating circularly polarized beams,” Appl Phys Lett, vol. 111, p. 224, 2017. in Google Scholar

[29] J. D. Elgin, T. P. Heavner, J. Kitching, E. A. Donley, J. Denney, and E. A. Salim, “A cold-atom beam clock based on coherent population trapping,” Appl Phys Lett, vol. 115, 2019, Art no. 033503. in Google Scholar

[30] G. W. Hoth, R. Elvin, M. W. Wright, B. Lewis, A. S. Arnold, P. F. Griffin, et al., “Impact of laser frequency noise in coherent population trapping with cold atoms,” in 2019 Joint Conf. of the European Frequency and Time Forum and IEEE International Frequency Control Symposium (EFTF/IFCS), 2019. (IEEE, Orlando, FL) in Google Scholar

[31] X. Liu, E. Ivanov, V. I. Yudin, J. Kitching, and E. A. Donley, “Low-drift coherent population trapping clock based on laser-cooled atoms and high-coherence excitation fields,” Phys Rev Appl, vol. 8, 2017, Art no. 054001. in Google Scholar

[32] Z. Warren, M. S. Shahriar, R. Tripathi, and G. S. Pati, “Experimental and theoretical comparison of different optical excitation schemes for a compact coherent population trapping Rb vapor clock,” Metrologia, vol. 54, p. 418, 2017. in Google Scholar

[33] R. Elvin, G. W. Hoth, Wright, M. W., et al., “Raman-Ramsey CPT with a grating magneto-optical trap,” European Frequency and Time Forum (EFTF). Turin, IEEE 2018, p. 61–64. [Accessed: 2018].Search in Google Scholar

[34] R. Boudot, S. Guerandel, E. de Clercq, N. Dimarcq, and A. Clairon, “Current status of a pulsed CPT Cs cell clock,” in 2009 IEEE Transactions on Instrumentation and Measurement, 2009, vol. 58, pp. 1217–1222. (IEEE, Boulder, CO) in Google Scholar

[35] M. Shuker, J. W. Pollock, V. I. Yudin, J. Kitching, and E. A. Donley, “Optical pumping, decay rates and light shifts of cold-atom dark states” arXiv:1909.02649 [physics.atom-ph], 2019. in Google Scholar

Received: 2020-05-29
Accepted: 2020-07-07
Published Online: 2019-09-07
Published in Print: 2020-11-26

© 2020 Walter de Gruyter GmbH, Berlin/Boston

Downloaded on 5.3.2024 from
Scroll to top button