Precision Measurements of Quantum Scattering Phase Shifts with a Juggling Fountain Clock

使用杂耍喷泉钟精确测量量子散射相移

• 批准号: 1311570
• 负责人: Kurt Gibble
• 金额: $ 33万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1311570&HistoricalAwards=false
• 关键词: Precision; Measurements; Quantum; Scattering; Phase

This experimental research program will make precision measurements of quantum scattering phase shifts of ultracold cesium (Cs) atoms in an atomic clock. The group has demonstrated these measurements with a new type of scattering experiment that scatters a cesium atom in a coherent superposition of its two clock states off atoms in a pure state at ultracold temperatures. Each clock state experiences an s-wave scattering phase shift and, by detecting only the scattered part of each atom's wavefunction, the difference of the scattering phase shifts is directly observed as a phase shift of Ramsey fringes. A unique feature is that the observed difference of the scattering phase shifts is independent of the atomic density, providing atomic clock accuracy to scattering measurements. With high precision, the group has observed a number of Feshbach resonances with two clouds colliding at energies between 10 and 50 microKelvin, and recently at collision energies of order 1 microKelvin, within a single cloud. They will perform a first accuracy demonstration, which is expected to significantly improve the knowledge of the Cs-Cs interactions. The scattering lengths are presently insufficiently known that they impact the accuracy and operational parameters of cesium clocks, particularly the Atomic Clock Ensemble in Space (ACES) clock scheduled to fly on the International Space Station. The group will evaluate systematic errors, principally due to backgrounds, and improve the precision of the phase measurements. An improved theoretical understanding can guide future measurements, potentially studying different angular momenta, versus energy and magnetic field, and for various internal states. The group will also collaborate with national labs around the world to improve the accuracy of the best atomic clocks. The group provides a unique expertise on the design of microwave cavities for primary atomic clocks and participates in the accuracy evaluation of primary atomic clocks. Ideas developed as part of the juggling experimental work provided the explanation of the interactions of ultracold fermions for optical lattice clocks, recently experimentally observed in a chip-scale atomic clock and with a radio frequency transition in Li-6 fermions. Accurate time keeping is crucial for navigation, communication, global positioning, and national security. Recent research of this group has significantly advanced the accuracy of the atomic clocks that contribute to International Atomic Time (TAI). Their contributions were essential to realize the currently most accurate atomic clock. Novel advancements by the research have reduced many large systematic errors that previously limited the performance of atomic clocks. Earlier work had led to rubidium being adopted as the first amendment to the definition of the International System of Units (SI) second, novel space clock designs, and an understanding of the frequency shifts due to ultracold collisions in precision measurements. The research will further advance the most accurate precision measurements and the understanding of ultracold atom-atom interactions. The training of graduate and undergraudate students in many areas of modern technology from lasers, electro-optics, radio-frequency and microwave techniques, and atomic clocks and frequency control, is important for the development of the nation's scientific workforce.

该实验研究项目将精确测量原子钟中超冷铯 (Cs) 原子的量子散射相移。该小组通过一种新型散射实验证明了这些测量结果，该实验在超冷温度下将铯原子以其两个时钟状态的相干叠加方式散射到纯状态的原子上。每个时钟状态都会经历一个 s 波散射相移，并且通过仅检测每个原子波函数的散射部分，可以直接观察到散射相移的差异作为拉姆齐条纹的相移。一个独特的功能是，观察到的散射相移差异与原子密度无关，从而为散射测量提供了原子钟精度。该小组高精度地观察到了许多费什巴赫共振，其中两个云在 10 到 50 微开尔文之间的能量碰撞，最近在单个云内以 1 微开尔文的碰撞能量观测到。他们将进行首次准确性演示，预计将显着提高对 Cs-Cs 相互作用的了解。目前对散射长度的了解还不够，它们会影响铯钟的精度和运行参数，特别是计划在国际空间站飞行的太空原子钟组合（ACES）时钟。该小组将评估主要由背景引起的系统误差，并提高相位测量的精度。改进的理论理解可以指导未来的测量，有可能研究不同的角动量、能量和磁场以及各种内部状态。该小组还将与世界各地的国家实验室合作，提高最好原子钟的准确性。该小组在初级原子钟微波腔体设计方面拥有独特的专业知识，并参与初级原子钟的精度评估。 作为杂耍实验工作的一部分而提出的想法提供了对光学晶格钟的超冷费米子相互作用的解释，最近在芯片级原子钟中实验观察到了这种相互作用，并与Li-6费米子中的射频跃迁进行了实验。准确的计时对于导航、通信、全球定位和国家安全至关重要。 该小组最近的研究显着提高了国际原子时（TAI）原子钟的准确性。他们的贡献对于实现目前最精确的原子钟至关重要。这项研究的新进展减少了许多以前限制原子钟性能的大型系统误差。 早期的工作导致铷被采用作为国际单位制（SI）第二定义的第一修正案，新颖的空间时钟设计，以及对精密测量中超冷碰撞引起的频移的理解。该研究将进一步推进最准确的精密测量和对超冷原子间相互作用的理解。在激光、电光、射频和微波技术、原子钟和频率控制等现代技术许多领域对研究生和本科生的培训对于国家科学队伍的发展非常重要。