Quantum effects in radiation-pressure-dominated optomechanical systems

下一代干涉引力波（GW）探测器，如先进的LIGO探测器，将受到GW波段几乎所有频率的量子噪声的限制：低频的辐射压力噪声和高频的散粒噪声。这种量子噪声极限（QNL）是由于极高的循环激光功率，除了缓解其他经典噪声源。研究量子噪声限制并找到规避它们的方法不仅对提高未来GW探测器的性能很重要，而且对研究宏观机械系统中的基本量子效应（如压缩和纠缠）也很重要。该奖项支持一项实验研究计划，以产生和表征由光与宏观机械系统相互作用产生的量子态，目的是更好地理解量子测量的基本限制，以及提高干涉引力波探测器的性能。该研究计划的核心是一个米级干涉仪，具有低质量悬挂镜，高循环功率和量子限制读出。实验将用于研究以下辐射压力诱导的现象，使用该单一设备的变体：(1)观察有源压缩，这是传统使用非线性光学介质的一种新颖替代方法，它依赖于光力学振荡器系统中散粒噪声和辐射-压力噪声相关性的基本量子力学。这是量子噪声主导的引力波干涉仪（如先进的LIGO探测器）中量子效应的标志之一，值得在原型干涉仪中进行研究。(2)观测宏观物体的基态冷却是可能的，因为辐射压力可以用来减少物体的运动而不引入热噪声——这是量子测量领域中一个非常追求的目标。(3)观察到由辐射压力引起的镜面运动与量子辐射场耦合引起的量子纠缠。(4)直接观测量子辐射压力噪声。先进的LIGO预计在其探测波段的最低部分受到量子辐射压力噪声的限制，研究这种噪声源与光力学系统的相互作用可能会揭示更深层次的理解，甚至新的物理。到目前为止，这些现象都没有在实验中观察到。这项研究计划的主要目的是进一步了解辐射压力主导干涉仪，这是下一代引力波探测器的一个重要特征。同样吸引人的是，在宏观机械振荡器系统中，由于光-机械耦合而探索量子相关的基本物理的前景。拟议工作的更广泛影响在于其科学和人员的多样性。科学多样性源于所提议的研究的必然的跨学科性质：它结合了量子光学和量子测量理论与引力波探测的技术和形式。人员的多样性是PI（她自己也是少数民族的一员）积极招募女性和少数民族学生的结果，通过她自己的努力以及LIGO实验室和麻省理工学院的外展项目。此外，次级质素基准的测量方法深受学生欢迎，市民亦对其有相当大的热情。该实验与量子隐形传态、量子信息、量子控制和凝聚态物理（纳米和微机械振荡器）具有共同的技术。

Next-generation interferometric gravitational-wave (GW) detectors, such as the Advanced LIGO detectors, will be limited by quantum noise at almost all frequencies in the GW band: radiation-pressure noise at low frequencies and shot noise at high frequencies. This quantum noise limit (QNL) is reached due to extremely high circulating laser power, in addition to mitigation of other classical noise sources. Studying quantum noise limits and finding ways to circumvent them is important not only for improved performance of future GW detectors, but also allows for the study of fundamental quantum effects, such as squeezing and entanglement, in macroscopic mechanical systems.This award supports an experimental research program to generate and characterize quantum states arising from the interaction of light with macroscopic mechanical systems, with the goal to better understand the fundamental limits of quantum measurement, as well as to improve the performance of interferometric gravitational-wave detectors. The centerpiece of the research program is a meter-scale interferometer with low-mass suspended mirrors, high circulating power, and a quantum-limited readout. Experiments will be conducted to study the following radiation pressure induced phenomena, using variants of this single apparatus: (1) Observation of ponderomotive squeezing, a novel alternative to the more traditional use of nonlinear optical media, that relies on the fundamental quantum mechanics of the shot noise and radiation-pressure noise correlations in an optomechanical oscillator system. This is one of the hallmarks of quantum effects in quantum-noise-dominated gravitational-wave interferometers, such as the Advanced LIGO detectors, and warrants studying in prototype interferometers. (2) Observation of ground state cooling of a macroscopic object is possible because radiation pressure can be used to reduce the motion of objects without introducing thermal noise---a much sought after goal in the realm of quantum measurement. (3) Observation of quantum entanglement, arising from radiation pressure induced coupling of the motion of the mirror and the quantum radiation field. (4) Direct observation quantum radiation pressure noise. Advanced LIGO is expected to be limited by quantum radiation pressure noise in the lowest part of its detection band, and studying the interaction of this noise source with the optomechanical system is likely to reveal deeper understanding, or even new physics. None of these phenomena have been observed experimentally to date. The main purpose of this research program is to gain further understanding of radiation-pressure dominated interferometers, an important feature of next-generation gravitational wave detectors. Equally attractive is the prospect of exploring the fundamental physics of quantum correlations due to optical-mechanical couplings in a macroscopic mechanical oscillator system. The broader impact of the proposed work lies in its scientific and its personnel diversity. The scientific diversity arises from the necessarily cross-disciplinary nature of the proposed research: it combines the techniques and formalism of quantum optics and quantum measurement theory with gravitational-wave detection. The personnel diversity is the outcome of aggressive recruitment of women and minority students by the PI (herself a member of minority groups), through her own efforts as well as those of the outreach programs of the LIGO Laboratory and MIT. In addition, the sub-QNL measurements are popular with students and generate considerable enthusiasm with the public as well. The proposed experiments share common technologies with quantum teleportation, quantum information, quantum control and condensed matter physics (nano- and micro-mechanical oscillators).