Quantum Optomechanics on Multiple Mass Scales

该奖项支持一项实验计划，该计划旨在产生和表征光与宏观机械振荡器相互作用产生的量子态，目的是进一步了解量子测量的基本极限，并改进干涉式引力波探测器的性能。两个主要的实验是：(I)一个米级干涉仪，1克反射镜作为钟摆悬挂，高循环功率，量子限制光学读出，和(Ii)厘米长的法布里-珀罗腔和一个低温冷却250纳克悬臂式微镜。这些实验的目标是：(1)直接观察量子辐射压力(Backaction)噪声；(2)观察和操纵光机耦合产生的光机诱导透明度；(3)观察有质运动压缩；(4)观察宏观物体的基态冷却；(5)达到并超过自由粒子的标准量子极限；(6)观察由于辐射压力引起的反射镜运动和量子辐射场的耦合而产生的量子纠缠。到目前为止，还没有在实验中观察到这些现象。这个项目的主要目的是加深对辐射压力主导的干涉仪的理解，这是未来引力波探测器的一个重要特征。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的前景。干涉引力波探测器，如激光干涉仪引力波天文台(LIGO)的那些，正在寻求探测由猛烈的宇宙事件发出的引力波，如超新星爆炸和中子星和黑洞的碰撞。由于引力波与电磁辐射完全不同，直接探测引力波有望打开一扇进入宇宙的新窗口，并为研究仅用光看不见的宇宙现象提供机会。来自天体物理来源的引力波会导致时空的微观扭曲，这可以通过干涉仪进行测量，干涉仪的镜面被悬挂成钟摆，以将它们与引力波以外的所有其他影响隔离开来。通过非常精确地测量从干涉仪的每个4公里长的臂反射的激光的干涉图案，可以检测到臂长度的变化，通常是质子大小的1/1000量级。由于光子的离散性质，光的量子涨落限制了引力波探测器的灵敏度。由于光的随机量子涨落，这种所谓的散粒噪声限制了干涉图案的测量精度，从而限制了引力波信号的测量。同样，辐射压力噪声限制了灵敏度，因为当激光从干涉仪反射镜反射时，传输到反射镜上的光子的波动动量会“踢”干涉仪反射镜。研究表征和绕过这一噪声极限的方法对于进一步提高引力波探测器的灵敏度是至关重要的，也可以用来研究宏观力学系统中的基本量子效应，如压缩和纠缠。这项研究计划更广泛的影响在于它的科学和人员多样性。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，亚量子噪声极限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信息、量子控制和介观凝聚态物理(纳米和微机械振荡器)的共同技术。

This award supports an experimental program to generate and characterize quantum states arising from the interaction of light with macroscopic mechanical oscillators, with the goal of furthering the understanding of the fundamental limits of quantum measurement, as well as improving the performance of interferometric gravitational-wave detectors. The two main experiments are: (i) a meter-scale interferometer with 1 gram mirrors suspended as pendulums, high circulating power, and a quantum-limited optical readout, and (ii) a centimeter-long Fabry-Perot cavity with a cryogenically cooled 250 nanogram cantilevered micromirror. The objectives of these experiments are: (1) Direct observation quantum radiation pressure (backaction) noise; (2) Observation and manipulation of optomechanically induced transparency that arises when optomechanical coupling introduces sufficient optical rigidity to renormalize the dressed mechanical states into optically-bright and optically-dark modes of motion; (3) Observation of ponderomotive squeezing; (4) Observation of ground state cooling of a macroscopic object; (5) Reaching and surpassing the free-particle Standard Quantum Limit; (6) Observation of quantum entanglement, arising from radiation pressure induced coupling of the motion of the mirror and the quantum radiation field. None of these phenomena have been observed experimentally to date. The main purpose of this program is to further the understanding of radiation-pressure-dominated interferometers, an important feature of future 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.Interferometric gravitational wave detectors, such as those of the Laser Interferometer Gravitational-wave Observatory (LIGO), are seeking to detect gravitational waves emitted by violent cosmic events such as supernova explosions and collisions of neutron stars and black holes. Since gravitational waves are completely distinct from electromagnetic radiation, direct detection of gravitational waves is expected to open a new window into the Universe and provide opportunities to study cosmic phenomena that are "invisible" using light alone. Gravitational waves from astrophysical sources cause microscopic distortions of spacetime that can be measured by an interferometer whose mirrors are suspended as pendulums to isolate them from all other effects beside the gravitational wave. The changes in arm length, typically of order 1/1000 the size of a proton, are detected by very precise measurement of the interference pattern of the laser light reflected from each 4 kilometer long arm of the interferometer. Quantum fluctuations of the light arising from the discrete nature of photons limit the sensitivity of gravitational wave detectors. This so-called shot noise, due to the random quantum fluctuations of the light, limits the precision with which the interference pattern, and hence the gravitational wave signal, can be measured. Similarly, radiation pressure noise limits the sensitivity due to the interferometer mirrors being "kicked" by the fluctuating momentum of the photons that is transferred to the mirrors when the laser light reflects from them. Studying ways to characterize and circumvent this noise limit is essential to making further improvements in sensitivity of gravitational wave detectors and also allows for the study of fundamental quantum effects, such as squeezing and entanglement, in macroscopic mechanical systems. The broader impact of this research program 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-quantum-noise-limit measurements are popular with students and generate considerable enthusiasm with the public as well. The proposed experiments share common technologies with quantum information, quantum control, and mesoscopic condensed matter physics (nano- and micro-mechanical oscillators).