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.

该实验研究计划将在原子钟中精确测量超冷铯（Cs）原子的量子散射相移。该小组已经通过一种新型的散射实验证明了这些测量，该实验在超冷温度下将铯原子的两个时钟状态相干叠加在纯原子上。每个时钟状态经历s波散射相移，并且通过仅检测每个原子的波函数的散射部分，散射相移的差被直接观察为拉姆齐条纹的相移。一个独特的特点是，所观察到的散射相移的差异是独立的原子密度，提供原子钟精度的散射测量。该小组以高精度观察到了两个云在10至50微开尔文之间碰撞的费什巴赫共振，最近在单个云内的碰撞能量为1微开尔文。他们将进行第一次准确性演示，预计将显着提高Cs-Cs相互作用的知识。散射长度目前还不足以影响铯原子钟的准确性和运行参数，特别是计划在国际空间站上飞行的太空原子钟（ACES）。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，可能研究不同的角动量，与能量和磁场，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，以提高最好的原子钟的准确性。该小组为原原子钟的微波腔设计提供独特的专业知识，并参与原原子钟的准确性评估。 作为杂耍实验工作的一部分开发的想法为光学晶格钟提供了超冷费米子相互作用的解释，最近在芯片级原子钟中进行了实验观察，并在Li-6费米子中进行了射频跃迁。准确的时间保持对于导航、通信、全球定位和国家安全至关重要。 该小组最近的研究大大提高了原子钟的准确性，为国际原子时（TAI）做出了贡献。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系统误差。 早期的工作导致铷被采纳为国际单位制（SI）定义的第一个修正案，第二，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率偏移的理解。这项研究将进一步推进最精确的测量和对超冷原子-原子相互作用的理解。对研究生和本科生进行激光、电光学、射频和微波技术、原子钟和频率控制等现代技术许多领域的培训，对国家科学工作者的发展至关重要。