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Cooling of an Optically Levitated Nanoparticle via Measurement-Free Coherent Feedback

Bruno Melo, Daniël Veldhuizen, Grégoire F. M. Tomassi, Nadine Meyer*, and Romain Quidant

  • Nanophotonic Systems Laboratory, Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland and Quantum Center, ETH Zurich, 8083 Zurich, Switzerland

  • *Contact author: nmeyer@ethz.ch
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Phys. Rev. Lett. 135, 213603 – Published 19 November, 2025

DOI: https://doi.org/10.1103/tl1k-56ly

Abstract

We demonstrate coherent, measurement-free optical feedback control of a levitated nanoparticle, achieving phonon occupations down to a few hundred phonons. Unlike measurement-based feedback, this all-optical scheme preserves the correlations between mechanical motion and the feedback signal. Adjustment of the feedback phase and delay provides precise and tunable control over the system dynamics. The ultimate cooling performance is currently limited by phase noise, which we analyze within a theoretical framework that outlines the constraints and prospects for reaching the motional ground state. Our results establish coherent feedback as a powerful tool for quantum control of levitated systems, extending beyond center-of-mass cooling.

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Phys. Rev. Lett. 135, 213603– Published 19 November, 2025
  • Received 26 June 2025
  • Revised 28 August 2025
  • Accepted 22 October 2025
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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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