基于氮化硅薄膜腔光力系统的非经典量子态制备与操控研究

Quantum optomechanics focuses on the research of quantum mechanical phenomenons and laws which describe the interaction between light fields and mechanical resonators. It has found potential applications in the fundamental tests of macroscopic quantum physics, ultrasensitive quantum measurement of the force and displacement, quantum information processing, etc. At present, most of the cavity optomechanics experiments which have been demonstrated operate in the regime of so called resolved sideband limit. However, for those mechanical resonators with relatively large dimensions and mass, their natural frequencies are low and the condition of the resolved sideband limit is hard to satisfy. In this project, we will study the cavity optomechanics system in the regime beyond the resolved sideband limit. More precisely, we will utilize a high quality NSi membrane as the mechanical resonator and cool the resonator to its quantum ground state in the unresolved sideband limit. On the basis of cooling, we will study new approaches and techniques for the preparations of nonclassical quantum states in the cavity optomechanics system. The high efficient coupling mechanism between the light fields and the mechanical modes will be investigated and exploited to generate both squeezed light fields and squeezed states of the mechanical mode. Quantum nondemolition measurements will also be studied and performed to monitor the quantum state of mechanical mode. The proposed project will promote the progress of the quantum optomechanics, and play a key role on ultrasensitive quantum measurement, test of macroscopic quantum physics, and quantum information processing.

量子光力是研究光场和机械振子相互作用的量子现象和规律的研究领域，在检验宏观量子物理，力、位移等物理量的超精密量子测量，量子信息处理等方面具有重要的应用价值。目前已实现的腔光力实验主要工作在可分辨边带区域，然而对于较大尺度和质量的机械振子，其本征振动频率很低，可分辨边带条件通常难以满足。本项目拟开展不可分辨边带区域腔光力系统的机械振子冷却与非经典量子态制备的实验与理论研究，拟利用高品质因子氮化硅薄膜作为机械振子，实验实现不可分辨边带情形下机械振子的基态冷却与高精度测量；在此基础上利用腔光力系统进行非经典量子态制备与操控的新方法与技术研究，通过高效光力相互作用机制实验制备出压缩态光场；研究光场-机械模的高效耦合与转换机制，实现低频机械振子压缩态的制备与非破坏性测量。本项目的实施将有效推动量子光力学的发展，对于超精密量子测量、宏观量子物理及量子信息处理具有重要意义。

量子光力是研究光场和机械振子相互作用的量子现象和规律的研究领域，在检验宏观量子物理，力、位移等物理量的超精密量子测量，量子信息处理等方面具有重要的应用价值。目前已实现的腔光力实验系统多数工作在可分辨边带区域，然而对于较大尺度和质量的机械振子，其本征振动频率很低，可分辨边带条件通常难以满足。本项目针对不可分辨边带区域腔光力系统的机械振子冷却与非经典量子态制备等进行了理论与实验研究，完成的主要研究内容和取得的重要结果如下：.在氮化硅薄膜的硅基片上设计了级联的低频谐振子结构，有效抑制了薄膜机械振子与支撑结构之间的声子损耗，制备出品质因子两百万以上的氮化硅薄膜机械振子；搭建了薄膜腔光力系统的反馈冷却实验平台，在3K低温下实现了薄膜机械振子接近基态的反馈冷却；研究了适当功率和失谐量的冷却光和信号光注入薄膜腔光力系统，通过光场辐射压力和机械运动的光力相互作用制备压缩态光场；提出利用单腔弱耦合腔光力系统通过受控的光力四波混频机制产生强量子纠缠光场的方案；提出利用光腔模式与机械振子的线性和非线性耦合作用机制制备高压缩度机械振子的实验方案，机械模式正交分量的压缩度可突破10 dB；通过对薄膜机械振子基片进行电激励，激发了机械振子多个机械模式之间的非线性参量作用，实验实现了机械振子基模的正交分量压缩以及（1,2）和（2,1）模式之间的双模压缩；提出在边带不可分辨区域实现光力四波混频的方案并在实验上验证，通过控制泵浦光的强度和失谐实现对四波混频过程的操控，利用四波混频效应实现了极弱信号光的高增益窄带低噪声放大。.本项目的实施促进了量子光力学的发展，对于超灵敏量子测量、宏观量子物理及量子信息处理具有重要意义。