Frequency metrology for precision measurements on matter-antimatter symmetry

在今天的宇宙中，反物质的虚拟缺失和物质的优势仍然是物理学面临的最大难题之一。早在1967年，著名的萨哈罗夫条件就描述了这个不对称宇宙是如何通过要求物质和反物质之间的对称性违背(即差异)来实现的。到目前为止，还没有发现足够的对称性破坏来解决这个问题，因此这个谜团仍然存在。这个项目旨在通过直接测试由反物质组成的原子的结构与其对应物质的结构无法区分的假设来寻求这个问题的答案。这项拨款建议安装一个铯喷泉原子钟，它将允许对反氢进行光谱测量，其不确定度与我们测量时间本身的精确度相称。该项目为我们的长期计划提供了最先进的设备，在长期计划中，我们使用这一最终的精密测量工具来解决反物质难题。我们的方法是捕获反氢原子(我们将反质子和正电子结合而成的原子)，以便使用原子物理学中的光谱技术来研究它们的内部结构。我们的工作为我们提供了迄今为止科学工具箱中最精确的量具，也是全球定位系统(GPS)的基础；原子钟。具体地说，我们研究了磁囚禁中反氢(反物质)的基态到第一激发态的跃迁，以检验这种跃迁的频率与氢(物质)的频率完全相同的假设。在氢气中，这种转变的研究精度达到了惊人的15位小数。我们最近在反氢方面达到了12位小数的精确度。要使我们的反物质功与物质实验的结果相匹配，我们需要确定反氢的1S-2S跃迁频率，并与氢气中相应的测量结果保持一致。新设备是一种最先进的原子钟，与使SI-秒的定义切实可行的类型相同。由于原子钟直接测量国际单位制中定义的铯的超精细间隔，它将给我们提供最好的绝对频率基准，并允许我们达到反物质物质所达到的精度。这个项目实现的反物质研究，测试了解释我们周围世界的物理学基础，并形成了日益复杂的基础技术。尽管取得了所有这些成功，我们仍然不明白为什么宇宙中似乎没有大量的反物质。在这个项目中，我们根据我们目前的理解，寻找与预期的微小偏差。经验表明，对自然的精确观察会导致我们对自然认识的突破。在这里，反氢是一个引人注目的主题，因为它的性质的非常具体的预测，以及已经获得的精确结果在它的物质对应。在这条道路上找不到新线索的风险，远远超过了不寻找它们的风险，而我们现在显然可以找到它们。可以归因于对称性破坏的反氢和氢之间的观测差异，将对物理学基础产生深远的、今天甚至是不可想象的后果。即使现在没有发现任何线索，对反氢性质的最精确的直接测量也有巨大的内在价值。

The virtual absence of antimatter and preponderance of matter in the Universe today remains one of the biggest conundrums facing physics. Already in 1967, the famous Sakharov conditions described how this asymmetric Universe could come about by requiring symmetry violations (i.e. differences) between matter and antimatter. Until now, no sufficient symmetry violations have been found to resolve this question, thus the puzzle remains. This project aims to seek answers to this question by directly testing the supposition that the structure of atoms made of antimatter is indistinguishable from the structure in their matter counterparts.This grant proposes the installation of a caesium fountain atomic clock which will allow spectroscopic measurements of antihydrogen with an uncertainty commensurate with how accurately we can measure time itself. This project provides state-of-the-art equipment for our long-term programme where we use this ultimate tool of precision measurements to address the antimatter conundrum. Our approach is to trap antihydrogen atoms, (atoms that we make by combining antiprotons and positrons) in order to study their internal structure using spectroscopic techniques from atomic physics. We draw from work that have given us the most precise gauges in the scientific toolbox to date and the basis for the global positioning system (GPS); atomic clocks. Specifically, we investigate the ground to first excited state transition in antihydrogen (antimatter) held in a magnetic trap to test the hypothesis that the frequency of this transition is exactly the same as that of hydrogen (matter). This transition has been investigated with a staggering 15 decimal places of precision in hydrogen. We have recently achieved a precision of 12 decimal places in antihydrogen. Improving our antimatter-work to match the result in matter experiments requires us to determine the antihydrogen 1S-2S transition frequency with the accuracy of the corresponding measurement in hydrogen. The new equipment is a state-of-the-art atomic clock identical to the type that makes the definition of the SI-second practical. Since the atomic clock directly measures the hyperfine interval in caesium as defined in the SI-system of units, it will give us the best possible absolute frequency reference and allow us to reach the precision achieved in matter with antimatter. The antimatter research that this project enables , tests the very foundations of physics that explains the world around us and forms the basis technology of increasing complexity. Despite all this success, we still do not understand why there appears to be no bulk antimatter in the Universe. In this project we look for tiny deviations from expectations based on our current understanding. Experience shows that precise observation of Nature leads to breakthroughs in our understanding. Here, antihydrogen is a compelling subject due to the very specific predictions of its properties, and the already available precise results in its matter counterpart. The risk of finding no new clues on this path is far outweighed by the risk of not looking for them when we now very clearly can. An observed difference between antihydrogen and hydrogen that can be attributed to symmetry breaking would have profound, today even unimaginable, consequences on the foundations of physics. Even if no clues are found now, there is immense intrinsic value in the most precise direct measurement of a property in antihydrogen.