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Levitated mechanical resonators have the potential to achieve low mechanical loss and high quality factor (Q factor), which is critical for many applications, e.g. high precision sensors, and exploring fundamental quantum physics. Diamagnetic levitation is a promising technique, which requires no energy input and can trap massive objects. However, conductive pyrolytic graphite, one of the strongest room-temperature diamagnetic materials, suffers severe eddy damping, leading to a very low Q factor. We explored different methods to increase the Q factor to satisfy a variety of applications. Firstly, we cut slots into the graphite plate to interrupt the eddy currents and the Q is increased by a factor of ∼ 40 while keeping the integrity of the plate itself.[1] In the second method, we make insulating composites by blending the insulating-coated graphite powders with vacuum-compatible wax. The cm-sized composite resonators achieve motional Q factor at the scale of 10^5.[2] We also cool the center-of-mass motion of the composite resonator by 3 orders of magnitude, using feedbacak method. In addition, we propose a cavity optomechanical system to reach the quantum ground state of a magnetically levitated mirror, by locking it to a fixed fiber Bragg mirror , using the Pound-Drever-Hall (PDH) technique.[3] These will enable us to engineer macroscopic superposition states to study quantum gravity and build ultra-precise accelerators.
1 P. Romagnoli et al., Appl. Phys. Lett. 122, 094102 (2023)
2 S. Tian et al., Appl. Phys. Lett. 124, 124002 (2024)
3 A. Hodges et al., Phys. Rev. A 113, 033508 (2026)