QuSeC-TAQS: Improving Geodesy and Gravitational Sensing with Quantum Sensors of Time

QuSeC-TAQS：利用量子时间传感器改进大地测量和重力感应

• 批准号: 2326808
• 负责人: Scott Diddams
• 金额: $ 189.98万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2326808&HistoricalAwards=false
• 关键词: QuSeC; TAQS; Improving; Geodesy; Gravitational

One of the more surprising predictions of Einstein’s theory of general relativity is that time evolves more slowly under the influence of gravity. Known as the gravitational redshift, the effect predicts that a clock further from the Earth will tick faster relative to one closer to the Earth. From the human perspective, the magnitude of the effect is small, but it has important impacts for GPS navigation, fundamental timekeeping, and as this project will show, for measuring gravity and the shape of the Earth. This concept is known as relativistic geodesy, and it employs the some of best optical clocks, which are advanced quantum sensors of time. Specifically, this project will use optical clocks and time transfer systems to advance geodesy beyond the state-of-the-art. This will involve transporting a cold-atom optical clock to the mountainous regions of Colorado to measure geopotential differences using relativistic geodesy, showing the value of precision timekeeping for measuring the shape of the Earth at the 1 cm level. This team also expects to make the best test of the gravitational redshift predicted by Einstein’s theory. The proposed effort uniquely explores how research and technologies from quantum, atomic, and laser physics can be better engineered and applied for the benefit of gravitational and geophysics through high temporal and spatial resolution measurements that will ultimately impact the fields of hydrology, mineral exploration, and seismology.A minimum requirement for relativistic geodesy is the ability to operate two optical clocks at distinct locations of interest, as well as a measurement link to observe the gravitational redshift between them. For the geodesy proposed here, this team will use an ytterbium optical lattice clock currently operating at NIST as the reference clock. This clock is located in the fixed gravitational reference frame, and has already demonstrated systematic uncertainty, frequency stability, and reproducibility at 1 part in a billion billion (10^18) or better. The second clock system will be a transportable optical clock, also based on ultracold ytterbium atoms in an optical lattice. In this program, the robustness of the transportable clock will be improved, and its systematic uncertainty will be fully evaluated to match that of the laboratory clock. The fixed and transportable clocks will then be compared via optical time transfer that relies on the two-way exchange of laser light from frequency combs across the air between NIST and the mountaintop. Ultimately, the transportable clock will be moved to a mountain summit (Mt. Evans, 14,264 feet) to perform relativistic geodesy. Direct line of sight from Mt. Evans to Boulder does not exist, so a two-arm link will be utilized that combines free-space laser link, followed by a fiber-optic based link from Broomfield to NIST Boulder. Connecting the pieces, this quantum-sensor-based geodesy measurement will yield accuracy at or below 2 cm. More significantly, the sizeable elevation difference between Mt. Evans and Boulder (2600 m) corresponds to a large gravitational redshift of nearly 3 parts in ten to the thirteen (10^13). Since the optical clocks can measure at the level of 2 parts in 10^18, the redshift will be resolved at 10 ppm level or better. Together with classical geopotential determination, this proposed measurement will yield the most precise test of the general relativistic redshift ever, either for terrestrial or space-based measurements.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.

爱因斯坦广义相对论中最令人惊讶的预测之一是，在引力的影响下，时间演化得更慢，这种效应被称为引力红移，它预测距离地球较远的时钟会比离地球较近的时钟走得更快。从人类的角度来看，这种效应的幅度很小，但它对 GPS 导航、基本计时以及测量重力和地球形状有重要影响。这个概念被称为相对论。具体来说，该项目将使用光学时钟和时间传输系统来推动大地测量学超越最先进的技术，这将涉及运输一个。该团队还期望在科罗拉多州山区使用冷原子光学时钟，利用相对论大地测量学测量地势差，展示精确计时对于测量地球形状的价值。爱因斯坦理论预测的引力红移独特地探索了如何通过高时间和空间分辨率测量更好地设计和应用量子、原子和激光物理学的研究和技术，以造福于引力和地球物理学。水文学、矿产勘探和地震学领域。相对论大地测量学的最低要求是能够在不同的感兴趣位置操作两个光学时钟，以及用于观察对于这里提出的大地测量，该团队将使用目前在 NIST 运行的镱光学晶格时钟作为参考时钟，该时钟位于固定引力参考系中，并且已经证明了系统不确定性、频率稳定性、再现性达到十亿分之一 (10^18) 或更高 第二个时钟系统将是一个可运输的光学时钟，也基于光学中的超冷镱原子。在该程序中，可移动时钟的鲁棒性将得到提高，并且其系统不确定性将得到充分评估，以匹配实验室时钟的系统不确定性，然后将通过依赖于两者的光学时间传递来比较固定时钟和可移动时钟。来自频率梳的激光在 NIST 和山顶之间进行双向交换，最终，可移动时钟将被移动到山顶（埃文斯山，14,264 英尺）以进行直接相对论大地测量。从埃文斯山到博尔德的视线不存在，因此将使用结合了自由空间激光链路的双臂链路，然后是从布鲁姆菲尔德到 NIST 博尔德的基于光纤的链路，将各个部分连接起来。 -基于传感器的大地测量将产生 2 厘米或以下的精度 更重要的是，埃文斯山和博尔德 (2600 米) 之间的巨大海拔差异对应于近乎的大重力红移。十到十三中的 3 个部分（10^13） 由于光学钟可以在 10^18 中的 2 个部分进行测量，因此红移将与经典位势测定一起在 10 ppm 或更好的水平上得到解决。测量将产生有史以来最精确的广义相对论红移测试，无论是对于陆地还是太空测量。该奖项反映了 NSF 的法定使命，并通过使用基金会的评估进行评估，被认为值得支持。智力价值和更广泛的影响审查标准。