Abstract
Feedback-based control of nano- and micromechanical resonators can enable the study of macroscopic quantum phenomena and also sensitive force measurements. Here, we demonstrate the feedback cooling of a low-loss and high-stress macroscopic SiN membrane resonator close to its quantum ground state. We use the microwave optomechanical platform, where the resonator is coupled to a microwave cavity. The experiment utilizes a Josephson traveling-wave parametric amplifier, which is nearly quantum-limited in added noise, and is important for mitigating resonator heating due to system noise in the feedback loop. We reach a thermal phonon number as low as 1.6, which is limited primarily by microwave-induced heating. We also discuss the sideband asymmetry observed when a weak microwave tone for independent readout is applied in addition to other tones used for the cooling. In a typical situation, the asymmetry can be attributed to the quantum-mechanical imbalance between emission and absorption. In specific situations, however, we find that the asymmetry is an artifact due to coupling of different sideband processes by cavity nonlinearity under multitone irradiation.
| Original language | English |
|---|---|
| Article number | 034009 |
| Journal | Physical Review Applied |
| Volume | 23 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - Mar 2025 |
| MoE publication type | A1 Journal article-refereed |
Funding
This work was supported by the Academy of Finland (contract 352189), and by the European Research Council (contract 101019712). The work was performed as part of the Academy of Finland Centre of Excellence program (contracts 352932, and 336810). We acknowledge funding from the European Union's Horizon 2020 research and innovation program under grant agreement 824109, the European Microkelvin Platform (EMP), and QuantERA II Programme (contract 13352189), and by the Beijing Municipal Science and Technology Commission (grant Z221100002722011). The work at VTT was supported in part by the Research Council of Finland through grant 321700 and through its Centres of Excellence program under grants 352934 and 336819, in part by the EU Flagship on Quantum Technology H2020-FETFLAG-2018-03 Project under grant 820363 OpenSuperQ, and in part by HORIZON-CL4-2022-QUANTUM-01-SGA Project under grant 101113946 OpenSuperQPlus100.