Frequency metrology for precision measurements on matter-antimatter symmetry

今天，宇宙中几乎不存在反物质，而物质占主导地位，这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破坏（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，因此这个难题仍然存在。该项目旨在通过直接测试由反物质组成的原子的结构与其物质对应物的结构无法区分的假设来寻求这个问题的答案。该资助建议安装一个铯喷泉原子钟，该原子钟将允许反氢的光谱测量，其不确定性与我们测量时间本身的准确性相称。该项目为我们的长期计划提供了最先进的设备，我们使用这种精确测量的终极工具来解决反物质难题。我们的方法是捕获反氢原子（我们通过结合反质子和正电子制造的原子），以便使用原子物理学的光谱技术研究它们的内部结构。我们借鉴了迄今为止为我们提供科学工具箱中最精确的仪表和全球定位系统（GPS）基础的工作;原子钟。具体来说，我们调查的地面第一激发态的反氢（反物质）在磁阱中举行的过渡，以测试的假设，这种过渡的频率是完全相同的氢（物质）。这种转变已经在氢中以惊人的15位小数的精度进行了研究。我们最近在反氢原子中达到了小数点后12位的精度。为了改进我们的反物质工作，使之与物质实验的结果相匹配，需要我们以氢中相应测量的精度来确定反氢1 S-2S跃迁频率。新设备是一个最先进的原子钟，与使SI秒的定义变得实用的类型相同。由于原子钟直接测量铯的超精细间隔，正如SI单位制所定义的那样，它将为我们提供最好的绝对频率参考，并使我们能够达到物质与反物质的精确度。该项目所支持的反物质研究，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理解的突破。在这里，反氢是一个引人注目的主题，因为它的性质非常具体的预测，以及它的物质对应物已经有了精确的结果。在这条道路上找不到新线索的风险远远超过了在我们现在非常清楚地可以找到新线索的时候不去寻找它们的风险。反氢和氢之间观测到的差异可以归因于对称性破缺，这将对物理学基础产生深远的、今天甚至难以想象的影响。即使现在还没有发现任何线索，对反氢的性质进行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.