Bera Tanmoy, Kandpal Mridul, Agarwal Girish S, Singh Vibhor
Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX, 77843, USA.
Nat Commun. 2024 Aug 19;15(1):7115. doi: 10.1038/s41467-024-51499-z.
Cavity-electromechanical systems are extensively used for sensing and controlling the vibrations of mechanical resonators down to their quantum limit. The nonlinear radiation-pressure interaction in these systems could result in an unstable response of the mechanical resonator showing features such as frequency-combs, period-doubling bifurcations and chaos. However, due to weak light-matter interaction, typically these effects appear at very high driving strengths. By using polariton modes formed by a strongly coupled flux-tunable transmon and a microwave cavity, here we demonstrate an electromechanical device and achieve a single-photon coupling rate of 160 kHz, which is nearly 4% of the mechanical frequency ω. Due to large g/ω ratio, the device shows an unstable mechanical response resulting in frequency combs in sub-single photon limit. We systematically investigate the boundary of the unstable response and identify two important regimes governed by the optomechanical backaction and the nonlinearity of the electromagnetic mode. Such an improvement in the single-photon coupling rate and the observations of microwave frequency combs at single-photon levels may have applications in the quantum control of the motional states and critical parametric sensing. Our experiments strongly suggest the requirement of newer approaches to understand instabilities.
腔机电系统被广泛用于传感和控制机械谐振器的振动，直至其量子极限。这些系统中的非线性辐射压力相互作用可能导致机械谐振器出现不稳定响应，表现出频率梳、倍周期分岔和混沌等特征。然而，由于光与物质的相互作用较弱，通常这些效应在非常高的驱动强度下才会出现。通过使用由强耦合磁通可调谐跨导器和微波腔形成的极化激元模式，我们在此展示了一种机电装置，并实现了160kHz的单光子耦合率，这几乎是机械频率ω的4%。由于较大的g/ω比，该装置显示出不稳定的机械响应，导致在亚单光子极限下出现频率梳。我们系统地研究了不稳定响应的边界，并确定了由光机械反作用和电磁模式的非线性所支配的两个重要区域。单光子耦合率的这种提高以及在单光子水平上对微波频率梳的观测可能在运动状态的量子控制和临界参数传感中具有应用价值。我们的实验强烈表明需要更新的方法来理解不稳定性。
