PM: Measuring Gravity at the Micron-Scale with Laser-Cooled Trapped Microspheres: A Renewal Proposal

引力是自然界中已知的四种基本力中最不为人所知的。 与其他三种标准模型力相比，它的弱点使得在实验中精确测量引力特别具有挑战性。粒子物理学标准模型之外的理论，包括弦论和超对称性，已经有几个预测，牛顿引力平方反比定律将在毫米尺度以下的某个距离处失效。为了检验这些理论，开发了一种使用光学捕获激光冷却玻璃珠作为测试质量和微加工硅和金器件作为源质量的方法。当被高真空环境包围时，玻璃珠经历非常小的摩擦，成为一种超精密的力测量仪器，需要测量物体之间在如此近的距离内的微弱引力相互作用。 同时，采用扫描和屏蔽方法来消除不期望的电磁背景力的系统影响。据估计，该方法可以提高搜索的引力平方反比定律在微米长度尺度的修正超过三个数量级。一名研究生和一名博士后研究员将接受实验物理和纳米纤维的广泛培训。通过参加这个高度跨学科的研究项目，学生将为科学事业做好充分的准备，并将努力将代表性不足的少数民族的研究人员包括在内。这个项目的基本性质可以向公众灌输对自然世界的好奇心。国家将受益于对与微米尺度引力物理学相关的高能物理学的更好理解，而粒子对撞机实验的成本只是一小部分。在这个项目中，将继续开发一个实验，利用激光冷却捕获微球测试Yukawa型偏离牛顿重力在微米长度尺度。这项新技术可以将对这种长度尺度的引力的理解提高三个数量级以上，并可能导致突破性的发现。基于先前的结果，包括校准的zeptonewton力灵敏度和开发技术，以可靠地在距离源质量表面微米距离内的三维空间中操纵纳米球，该项目的下一阶段在概念上分为两个任务：（1）初步重力测量中的系统误差调查，其目标是在专用的Yukawa力搜索中获得数百万个101 μ m尺度的综合数据，以及（2）并行开发用于捕获和冷却悬浮纳米颗粒的新方法，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Gravity is the least well understood of the four known fundamental forces in Nature. Its weakness when compared to the other three Standard Model forces makes gravity particularly challenging to measure precisely in experiments. There have been several predictions from theories beyond the Standard Model of particle physics, including string theory and supersymmetry, that the Newtonian gravitational inverse square law will break down at some distance below the millimeter scale. To put these theories to the test, a method using an optically-trapped laser-cooled glass bead as a test mass and a microfabricated silicon and gold device as a source mass has been developed. When surrounded by a high-vacuum environment, the glass bead experiences very little friction and becomes an ultraprecise force measurement instrument, needed to measure feeble gravitational interactions between objects at such close ranges. At the same time, scanning and screening methods are employed to eliminate systematic effects from undesired electromagnetic background forces. It is estimated that the method can improve the search for corrections to the gravitational inverse square law at the micron length scale by more than three orders of magnitude. One graduate student and one postdoctoral researcher will be broadly trained in experimental physics and nanofabrication. By participating in this highly interdisciplinary research project, students will be well equipped for scientific careers, and efforts to include researchers from under-represented minorities will be undertaken. The fundamental nature of this project can instill a sense of wonder about the natural world in the general public. 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. In this project, an experiment will continue to be developed which makes use of laser-cooled trapped microspheres to test for Yukawa-type deviations from Newtonian gravity at the micron length scale. This new technique can advance the understanding of gravity at this length scale by over three orders of magnitude and may lead to ground-breaking discoveries. Building on previous results, including calibrated zeptonewton force sensitivity and the development of techniques to reliably maneuver nanospheres in three-dimensions within micron-distances from a source mass surface, the next phase of the project is conceptually divided into two tasks: (1) investigation of systematic errors in preliminary gravity measurements, with a goal of acquiring millions of integrated data in a dedicated Yukawa-force search at the ∼ 1 μm-scale, and (2) in-parallel development of novel methods for trapping and cooling the levitated nanoparticles, including sympathetic cooling with cold atoms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.