Quantum Cavity Optomechanics

这项工作旨在将微机械系统带入完全量子状态，这将导致光学/纳米机械系统领域的突破。这将极大地拓宽我们对哪些物理系统可以表现出量子效应的概念，并允许我们在一种全新类型的系统(即机械系统)中探索与量子光学和介观凝聚态相关的物理学，这种系统与读出设备和环境的耦合在性质上与当今的量子系统不同。该项目使用超敏感的毫米级薄膜分散耦合到高精细度的光学腔中。这种耦合足够强，足以将薄膜激光冷却到其振动基态，观察到位移测量的量子反作用，并产生压缩光。同时，这种耦合可以被调谐到从光学机械系统中产生特别微妙的量子效应；通过实现强大的位置平方读出，我们将观察到薄膜振动中的能量量子化和薄膜能量本征态之间的量子跃迁。这些目标涵盖了广泛的概念范围，但它们代表了可以在单个设备中实现的同一光学机械耦合的不同方面。这些实验与各种领域的超灵敏仪器有关。量子有限位移测量与天体物理引力波搜索有关，压缩光的产生也是如此。冷却到基态的微机械设备可以作为异常灵敏的探测器，特别是当连接到能够记录设备的单个量子激发的读取器时。这些系统在概念上的简单性，再加上它们在宏观尺度上探索奇异量子现象的可能性，使它们具有吸引力。在过去的几年里，在这一领域工作的学生、博士后和PI的数量迅速增加，科学和普通受众的兴趣也越来越高。这项工作将为培养本科生、研究生和博士后掌握重要的科学技术奠定良好的基础，并将为他们在广泛的应用或基础研究领域的职业生涯做好准备。

This work is aimed at bringing a micromechanical system into the fully quantum regime, which would result in a breakthrough in the field of opto/nanomechanical systems. It would greatly broaden our notion of which physical systems can exhibit quantum effects and allow us to explore the physics associated with quantum optics and mesoscopic condensed matter in an entirely new type of system (i.e., mechanical), whose coupling to readout devices and the environment is qualitatively different from present-day quantum systems. The project uses ultrasensitive millimeter-scale membranes dispersively coupled to high-finesse optical cavities. This coupling is strong enough to laser-cool the membrane to its vibrational ground state, to observe the quantum back-action of displacement measurements, and to produce squeezed light. At the same time this coupling can be tuned to coax especially subtle quantum effects from the optomechanical system; by realizing a strong "position squared" readout we will observe the quantization of energy in the membrane's vibration and quantum jumps between the membrane's energy eigenstates. These goals cover a wide conceptual range, but they represent different facets of the same optomechanical coupling which can be realized in a single device. These experiments are relevant to ultrasensitive instruments in a variety of fields. Quantum limited displacement measurements are relevant to astrophysical gravitational wave searches, as is the production of squeezed light. Micromechanical devices cooled to their ground state could serve as exceptionally sensitive detectors, particularly when coupled to a readout capable of registering the devices' individual quantum excitations. The conceptual simplicity of these systems, combined with the possibility of using them to explore exotic quantum phenomena on a macroscopic scale makes them appealing. The past few years have seen a rapid increase in the number of students, postdocs, and PIs working in this field, and an increased level of interest from scientific and general audiences. This work will serve as an excellent basis for training undergraduate, graduate, and postdoctoral students in important scientific techniques, and will prepare them for a wide range of careers in applied or fundamental research.