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Λ-enhanced gray-molasses cooling of Rb85 atoms in tweezers using the D2 line

D. A. Janse van Rensburg*, R. C. Venderbosch*, Y. van der Werf, J. J. del Pozo Mellado, M. L. Venderbosch, R. S. Lous, E. J. D. Vredenbregt, and S. J. J. M. F. Kokkelmans

  • *These authors contributed equally to this work.
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Phys. Rev. A 113, 033123 – Published 26 March, 2026

DOI: https://doi.org/10.1103/tyxj-hb4l

Abstract

We demonstrate the implementation of Λ-enhanced gray molasses cooling on the D2 line of Rb85 atoms in an optical tweezer array. This technique yields lower atomic temperatures of 4.0(2) µK compared with red-detuned polarization gradient cooling, and consequently extends the T2* coherence time of the hyperfine clock qubit by a factor of 1.5. The method is alignment-free and can be readily implemented on laser beams used for magneto-optical trapping because it only requires frequency and phase modulation control. Our experimental observations are corroborated by a numerical model based on a semiclassical force approach extended to a four-level system, including two hyperfine states of the upper manifold that are 120MHz apart.

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Phys. Rev. A 113, 033123– Published 26 March, 2026
  • Received 23 December 2025
  • Accepted 10 March 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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