Low Noise Suspensions and Readout Systems for Improving Advanced LIGO

这是Vladimir Braginsky的莫斯科国立大学（MSU）小组和激光干涉引力波天文台（LIGO）实验室之间的合作研究项目。它着重于先进的LIGO正在考虑的两种增强：使用晶体硅作为干涉仪反射镜来减少热噪声，以及量子测量技术，可以提供超过当前限制的灵敏度，因为量子（射）噪声。众所周知，晶体硅具有优异的机械性能，其热膨胀最小值在120k附近。在这一点上的操作将最小化热噪声。然而，对于大规模应用来说，许多方面还没有得到很好的理解。在这项资助下，我们探索了为工作在120 K下的硅测试质量悬架制造硅带的技术，测量了硅带悬架的耗散，并找到了最小化硅悬架耗散和热噪声的方法。我们研究了纯高欧姆晶体硅和其他可能的候选材料在室温到液氮温度下的光学损耗和其他测量不良的热、机械和光学性能。最后分析了用于硅测试质量的晶体涂层的噪声源。高级LIGO灵敏度的另一个主要限制将是量子（射）噪声。我们还继续研究激光引力波探测器的新拓扑和测量方案，与增强型高级LIGO和其他相关，使我们能够抑制量子噪声并放宽对循环光功率的要求。这项工作的结果有许多影响。最直接的原因是，所开发的技术可以用来提高引力波探测器的灵敏度，从而有助于获得有关引起引力波的天体物理现象的更多信息。了解产生引力波的不寻常条件可以提高我们对塑造宇宙的暴力过程的理解，这让学生和公众感到兴奋和鼓舞。更广泛地说，在这项研究下开发的相同技术可以用于科学和工程中的许多精密测量应用。其中包括降低精密频率参考标准中的噪声以产生更精确的时钟，使量子密码学和量子计算更加可行，改进对空间和物质基本假设的测试，以及……最后，这项工作的一个主要目标是促进俄罗斯和美国科学家之间在和平研究方面的更密切合作。这促进了这两个超级大国的科学界之间更好的理解。

This is a collaborative research program between Vladimir Braginsky's Moscow State University (MSU) group and the Laser Interferometer Gravitational-Wave Observatory (LIGO) Laboratory. It focuses on two types of enhancements under consideration for Advanced LIGO: the use of crystalline silicon for the interferometer mirrors to reduce thermal noise, and quantum measurement techniques that can give sensitivities beyond the current limits due to quantum (shot) noise. Crystalline silicon is known to have excellent mechanical properties and has a minimum in its thermal expansion near 120 K. Operation at this point would minimize thermal noise. However, many aspects are not yet well enough understood for large scale application. Under this grant, we explore techniques for fabricating silicon ribbons for a silicon test mass suspension operating at 120 K, measure dissipation in silicon ribbon suspensions, and to find ways of minimization dissipation and thermal noise in the silicon suspensions. We investigate optical losses and other poorly measured thermal, mechanical and optical properties of pure high-ohmic crystalline silicon and other possible candidate materials for test masses from room to liquid nitrogen temperatures. Finally we analyze sources of noise in crystalline coatings applied to silicon test masses. The other main limitation to the sensitivity of Advanced LIGO will be quantum (shot) noise. We also continue the investigation of new topologies and measurement schemes for laser gravitational wave detectors, relevant to both Enhanced Advanced LIGO and beyond, and allowing us to suppress quantum noise and to relax requirements for the circulating optical power. The results of this work have a number of impacts. The most direct is that the techniques developed can be used to make gravitational wave detectors more sensitive, and thus help derive more information about the astrophysical phenomena that cause gravitational waves. Understanding the unusual conditions that create gravitational waves improves our understanding of violent processes that shape our universe exciting and inspiring students and the public. More broadly, the same techniques which are developed under this research can be used in a number of precision measurement applications in science and engineering. These include reducing noise in precison frequency reference standards to produce more accurate clocks, making quantum cryptography and quantum computing more feasible, improved tests of fundamental assumptions about space and matter, and ... finally, a major goal of this work is to foster closer collaboration on peaceful research between Russian and US scientists. This promotes better understanding between the scientific communities in these two super-powers.