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.

该实验研究计划将对原子钟中超速剖宫产（CS）原子的量子散射相移的精确测量。该小组通过一种新型的散射实验证明了这些测量值，该实验在其两个时钟状态的连贯叠加中散射剖腹原子，在超低温度下以纯状态下的原子。每个时钟状态都会经历S波散射相移，并且仅检测每个原子波函数的散射部分，直接观察到散射相移的差异是Ramsey Fringes的相移。一个独特的特征是，观察到的散射相偏移的差异与原子密度无关，从而为散射测量提供了原子时钟的精度。高精度，该组已经观察到许多Feshbach共振，两个云在10到50 microkelvin之间的能量碰撞，最近在单个云中的1 microkelvin订单1 microkelvin的碰撞能量。他们将进行第一个准确性演示，预计将显着提高CS-CS相互作用的知识。目前，散射长度不足以影响它们影响铯时钟的准确性和操作参数，尤其是计划在国际空间站飞行的太空时钟（ACES）时钟的原子钟集合（ACES）。该小组将主要由于背景而评估系统错误，并提高相测量的精度。改进的理论理解可以指导未来的测量值，潜在地研究不同的角动量，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，以提高最佳原子钟的准确性。该小组提供了针对主要原子钟的微波腔设计的独特专业知识，并参与了对原子钟的准确评估。 作为杂耍实验工作的一部分而开发的想法为光学晶格时钟的超速费米子的相互作用提供了解释，最近在芯片尺度的原子钟中观察到了实验，并在li-6 fermions中进行了射频过渡。准确的时间保持对于导航，沟通，全球定位和国家安全至关重要。 该小组的最新研究显着提高了有助于国际原子时间（TAI）的原子钟的准确性。他们的贡献对于实现当前最准确的原子钟至关重要。研究的新进步减少了许多大型系统错误，这些错误以前限制了原子钟的性能。 较早的工作导致rubidium被用作国际单位系统（SI）的定义的第一修正案，第二个新型太空时钟设计，以及对精确测量中超速碰撞引起的频移的理解。这项研究将进一步提高最准确的精度测量以及对超低原子 - 原子相互作用的理解。从激光器，电启动，射频和微波技术以及原子钟和频率控制的许多现代技术领域的研究生和涂鸦学生的培训对于发展国家科学劳动力很重要。