Active laser cooling of a centimeter-scale torsional oscillator
arXiv:2409.02275 · doi:10.1364/OPTICA.548098
Abstract
Experimental tests of gravity's fundamental nature call for mechanical systems in the quantum regime while being sensitive to gravity. Torsion pendula, historically vital in studies of classical gravity, are ideal for extending gravitational tests into the quantum realm due to their inherently high mechanical quality factor, even when mass-loaded. Here, we demonstrate laser cooling of a centimeter-scale torsional oscillator to a temperature of 10 mK (average occupancy of 6000 phonons) starting from room temperature. This is achieved by optical radiation pressure forces conditioned on a quantum-noise-limited optical measurement of the torsional mode with an imprecision 9.8 dB below its peak zero-point motion. The measurement sensitivity is the result of a novel `mirrored' optical lever that passively rejects extraneous spatial-mode noise by 60 dB. The high mechanical quality () and quantum-noise-limited measurement imprecision demonstrate the necessary ingredients for realizing the quantum ground state of torsional motion -- a pre-requisite for mechanical tests of gravity's alleged quantum nature.
References in corpus (10)
- Test of the Equivalence Principle Using a Rotating Torsion Balance
- Levitodynamics: Levitation and control of microscopic objects in vacuum
- Feedback cooling of a cantilever's fundamental mode below 5 mK
- Full Rotational Control of Levitated Silicon Nanorods
- Optical cold damping of neutral nanoparticles near the ground state in an optical lattice
- Simultaneous cooling of all six degrees of freedom of an optically levitated nanoparticle by elliptic coherent scattering
- Testing the quantum nature of gravity without entanglement
- Distinguishable consequence of classical gravity on quantum matter
- Quantum theory of feedback cooling of an anelastic macro-mechanical oscillator
- Microscale torsion resonators for short-range gravity experiments