Kavli Affiliate: Simon Groblacher
| First 5 Authors: Jingkun Guo, Jin Chang, Xiong Yao, Simon Gröblacher,
| Summary:
Preparing a massive mechanical resonator in a state with quantum limited
motional energy provides a promising platform for studying fundamental physics
with macroscopic systems and allows to realize a variety of applications,
including precise sensing. While several demonstrations of such ground-state
cooled systems have been achieved, in particular in sideband-resolved cavity
optomechanics, for many systems overcoming the heating from the thermal bath
remains a major challenge. In contrast, optomechanical systems in the
sideband-unresolved limit are much easier to realize due to the relaxed
requirements on their optical properties, and the possibility to use a feedback
control schemes to reduce the motional energy. The achievable thermal
occupation is ultimately limited by the correlation between the measurement
precision and the back-action from the measurement. Here, we demonstrate
measurement-based feedback cooling on a fully integrated optomechanical device
fabricated using a pick-and-place method, operating in the deep
sideband-unresolved limit. With the large optomechanical interaction and a low
thermal decoherence rate, we achieve a minimal average phonon occupation of
0.76 when pre-cooled with liquid helium and 3.5 with liquid nitrogen.
Significant sideband asymmetry for both bath temperatures verifies the quantum
character of the mechanical motion. Our method and device are ideally suited
for sensing applications directly operating at the quantum limit, greatly
simplifying the operation of an optomechanical system in this regime.
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