Measuring Gravity at the Micron Scale with Laser-Cooled Trapped Microspheres: a Continuation Proposal

引力是自然界最鲜为人知的基本力：量子引力的能量尺度与电磁力和核力的能量尺度相差16个数量级。这个谜团可以用另一种方式来解释：为什么引力要弱得多？正如最近的一些理论所表明的那样，通过测量重力在亚毫米距离内的行为，可以获得与这个“等级问题”有关的重要线索。这样的测量可能会带来令人兴奋的物理新发现，超出我们目前的知识。然而，随着质量物体的大小和间隔距离的变化，它们之间的引力很快就会变得很弱，因此在亚毫米尺度上进行超灵敏测量是必要的。该小组正在开发一项基于新技术的实验，该实验可以在微米长度尺度上将我们对重力的理解提高几个数量级。在这种方法中，测试质量被悬浮在由光制成的“容器”中，从而极大地减少了摩擦并提高了灵敏度。这项研究计划处于当前知识的前沿，并将提高内华达州的科学能力，目前内华达州在科学努力方面的代表性不足。与斯坦福大学的研究人员以及NSF赞助的斯坦福纳米制造设施的合作将改善该州的研究基础设施，为未来涉及纳米技术的合作开辟新的道路。学生和博士后研究人员将接受实验物理和纳米制造方面的广泛培训，并将为进入科学工作大军做好准备。这个项目的基本性质吸引了我们对自然世界的好奇感。日本将受益于对与微米尺度的引力物理相关的高能物理的更好理解，而成本只是粒子对撞机实验的一小部分。该奖项支持一项实验工作，该实验的目标是使用激光冷却的囚禁微球来测试微米尺度上的汤川类型的牛顿引力偏差。通过光学悬浮力传感器，可以实现与环境的精致解耦，潜在地产生亚阿顿力敏感度。这项新技术最终可以将我们对微米尺度引力的理解提高10万倍或更多，深入参数空间，从理论上预测与牛顿引力的偏差。除了对短程引力的研究外，我们提出的实验技术还可以对未知区域的卡西米尔力进行新的研究。该项目概念性地分为三个任务：(1)捕获冷却微球的力灵敏度的校准和优化；(2)源质量及其驱动机制的最终组装；(3)初步重力测量中的系统误差研究。我们还将研究冷却悬浮纳米球的新方法，包括用冷原子进行共振冷却。将开发一门研究生物理课程“混合量子系统”，以补充和加强拟议的研究，为推动科学发展带来新的想法和机会，同时发展学生在STEM主题方面的广度和专业知识。该奖项得到了引力物理和原子、分子和光学物理项目的支持。

Gravity is the least understood fundamental force of nature: there is a 16 order of magnitude disparity between the energy scale of quantum gravity and that of the electromagnetic and nuclear forces. The mystery can be cast in another way: why is gravity so much weaker? As a number of recent theories have suggested, important clues related to this "hierarchy problem" can be obtained by measuring how gravity behaves at sub-millimeter distances. Such measurements could lead to exciting new discoveries of physics beyond our current knowledge. However, the gravitational force between massive objects becomes weak very rapidly as their size and separation distance changes, thus making ultra-sensitive measurements a necessity at sub-millimeter length scales. This group is developing an experiment based on new technology which could advance our understanding of gravity by several orders of magnitude at the micrometer length scale. In this approach, a test mass is suspended in a "container" made of light, leading to greatly reduced friction and enhanced sensitivity. This research program is at the forefront of current knowledge and will enhance the scientific competency of the state of Nevada, which is currently under-represented in terms of scientific endeavor. The collaboration with researchers at Stanford and the NSF-sponsored Stanford Nanofabrication facility will improve the research infrastructure for the state, opening new pathways for future collaborations involving nanotechnology. Students and postdoctoral researchers will be broadly trained in experimental physics and nanofabrication and will be well positioned for entry into the scientific workforce. The fundamental nature of this project appeals to our sense of wonder about the natural world. The nation will benefit from an improved understanding of high-energy physics related to gravitational physics at the micron-length scale, at a fraction of the cost of particle-collider experiments.This award supports work on an experiment with the goal of using laser-cooled trapped microspheres to test for Yukawa-type deviations from Newtonian gravity at the micron length scale. By optically levitating the force sensor, an exquisite decoupling from the environment is possible, potentially yielding sub-attonewton force sensitivity. This new technique could ultimately advance our understanding of gravity at the micron length scale by a factor of 100,000 or more, probing deep into the parameter space for theoretically predicted deviations from Newtonian gravity. In addition to studies of short-range gravitational forces, the experimental technique we propose could also enable novel investigations of Casimir forces in unexplored regimes. The project is conceptually divided into three tasks: (1) calibration and optimization of the force sensitivity of the trapped cooled microspheres, (2) final assembly of the source mass and its driving mechanism, (3) investigation of systematic errors in preliminary gravity measurements. We will also investigate novel methods for cooling the levitated nanospheres, involving sympathetic cooling with cold atoms. A graduate physics course "Hybrid Quantum Systems" will be developed to complement and augment the proposed research, leading to new ideas and opportunities for advancing science, while developing students' breadth and expertise in STEM topics. This award is supported by the Gravitational Physics and the Atomic, Molecular and Optical Physics programs.