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Cooling of an Optically Levitated Nanoparticle via Measurement-Free Coherent Feedback
Bruno Melo1, Daniël Veldhuizen1, Grégoire F M Tomassi1
1ETH Zurich, Nanophotonic Systems Laboratory, Department of Mechanical and Process Engineering, 8092 Zurich, Switzerland and Quantum Center, ETH Zurich, 8083 Zurich, Switzerland.
Physical Review Letters
|December 5, 2025
Summary
This study introduces a novel all-optical feedback method for controlling levitated nanoparticles, achieving significant cooling without direct measurement. This technique preserves crucial correlations for advanced quantum control applications.
Area of Science:
- Quantum optics
- Nanomechanics
- Quantum control
Background:
- Levitated nanoparticles offer isolated quantum systems.
- Measurement-based feedback can disrupt quantum correlations.
- Precise control is needed for quantum state preparation.
Purpose of the Study:
- To demonstrate measurement-free optical feedback for levitated nanoparticles.
- To investigate the preservation of mechanical motion and feedback signal correlations.
- To analyze the limitations and potential for ground-state cooling.
Main Methods:
- Implementing a coherent, all-optical feedback loop.
- Utilizing adjustable feedback phase and delay.
- Developing a theoretical framework to analyze phase noise limitations.
Main Results:
- Achieved phonon occupations in the hundreds.
- Demonstrated tunable control over system dynamics.
- Identified phase noise as the primary limitation for ground-state cooling.
Conclusions:
- Coherent feedback is a powerful, measurement-free tool for quantum control.
- This method preserves quantum correlations, unlike measurement-based approaches.
- The technique shows promise for advancing quantum control beyond center-of-mass cooling.
