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。这一量子噪声极限(QNL)是由于极高的循环激光功率，加上其他经典噪声源的缓解。研究量子噪声极限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，而且有助于研究宏观机械系统中的基本量子效应，如压缩和纠缠。该奖项支持一项实验研究计划，该计划旨在产生和表征光与宏观机械系统相互作用产生的量子态，目的是更好地了解量子测量的基本极限，以及提高干涉型引力波探测器的性能。该研究计划的核心是一种米级干涉仪，它具有低质量的悬浮镜、高循环功率和量子限制读数。我们将用这个单一装置的变种来进行实验，以研究下列辐射压力诱导现象：(1)有质动力压缩的观测，这是一种更传统的使用非线性光学介质的新方法，它依赖于光机械振荡器系统中散粒噪声和辐射压力噪声关联的基本量子力学。这是以量子噪声为主的引力波干涉仪中量子效应的标志之一，例如先进的LIGO探测器，因此有必要研究原型干涉仪。(2)观测宏观物体的基态冷却是可能的，因为辐射压力可以在不引入热噪声的情况下减少物体的运动-这在量子测量领域是一个备受追捧的目标。(3)观察到由辐射压力引起的反射镜运动与量子辐射场的耦合所产生的量子纠缠。(4)直接观测量子辐射压强噪声。先进的LIGO有望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学机械系统的相互作用可能会揭示更深层次的理解，甚至是新的物理。到目前为止，还没有在实验中观察到这些现象。这项研究计划的主要目的是进一步了解辐射压力为主的干涉仪，这是下一代引力波探测器的重要特征。同样吸引人的是探索宏观机械振子系统中由于光-机械耦合而产生的量子关联的基本物理学的前景。拟议工作的更广泛影响在于其科学和人员多样性。科学多样性源于拟议研究的必然跨学科性质：它将量子光学和量子测量理论的技术和形式主义与引力波探测结合在一起。人员多样性是国际学生联合会(她自己也是少数群体成员)积极招募妇女和少数族裔学生的结果，她自己以及LIGO实验室和麻省理工学院的外联计划都是这样做的。此外，次级QNL测量在学生中很受欢迎，也在公众中产生了相当大的热情。拟议中的实验共享量子隐形传态、量子信息、量子控制和凝聚态物理(纳米和微机械振荡器)的共同技术。

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).