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Sub-kHz mechanical resonator passively cooled to 6 mK

Loek van Everdingen1,*, Jaimy Plugge1,*, Tim M. Fuchs1,2, Guido L. van de Stolpe1,3, Dalal Benali1, Thijmen de Jong1, Jasper Bijl1, Wim A. Bosch4, and Tjerk H. Oosterkamp1,†

  • 1Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands
  • 2School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, United Kingdom
  • 3E. L. Ginzton Laboratory, Stanford University, 348 Via Pueblo, Stanford, California, USA
  • 4HDL, Hightech Development Leiden, Leiden, The Netherlands

  • *These authors contributed equally to this work.
  • †Contact author: oosterkamp@physics.leidenuniv.nl
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Phys. Rev. Research 8, L022004 – Published 1 April, 2026

DOI: https://doi.org/10.1103/jmyg-299x

Abstract

Highly coherent mechanical resonators are invaluable to ultrasensitive detection techniques by enabling detection of small forces. Studying mechanical resonators in a thermal equilibrium state at millikelvin temperatures provides a promising path to increase their coherence time. Here, we passively cool a 700Hz massive (1.5ng) mechanical cantilever down to 6.1(4)mK by means of nuclear demagnetization, as confirmed by detecting its thermal motion via a lock-in-based detection scheme. At the lowest temperatures the thermal motion of the resonator is still clearly distinguishable from the background noise. Our data analysis confirms that at these temperatures, the motion is still thermally distributed. These results pave the way for passive cooling low-frequency resonators to the sub-millikelvin regime, which would enable tests of quantum mechanics and advances in ultrasensitive force detection.

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Phys. Rev. Research 8, L022004– Published 1 April, 2026
  • Received 28 October 2025
  • Accepted 31 December 2025
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