Light ion sympathetic cooling for precision measurements

在过去的二十年中，在限制在射频陷阱中的离子的量子态控制方面取得了惊人的进展。已经开发了将外部运动激光冷却到振动基态的方法。感应冷却将这些技术扩展到许多不能直接激光冷却的原子和分子物种。离子传输的进展允许在单独的、特别优化的陷阱中执行每个任务。因此，捕获离子现在代表了量子信息和高精度测量领域最先进的系统之一。该项目旨在克服这些技术的两个重要开放问题，这两个问题仍然阻碍了对高度有趣的光离子物种的研究。首先，上述结果是由电子冲击或光电离直接在阱内产生的离子获得的。然而，许多物种，如反物质离子，状态选择的分子离子，或高电荷离子是在外部来源产生的。我们计划开发一种通用装置，用于传输、捕获和冷却外部产生的离子。第二个挑战来自于交感冷却过程，对于多普勒和基态冷却，随着激光冷却和交感冷却物质的电荷质量比（q/m）的差异增加，其效率会降低。我们将通过实验研究高q/m差异下的交感冷却动力学，并开发专门适用于这种情况的冷却方法和陷阱几何形状。第一个申请是2012年CERN接受的GBAR项目；它涉及通过中性反氢原子的自由落体实验对反物质等效原理的第一次测试。目前项目的两个合作伙伴都是这个国际合作的14个成员之一，并且参与了关键步骤：Hbar+/Be+离子对中反氢正离子的基态冷却。我们的目标是交付GBAR实验的核心，完成Hbar+捕获和冷却的设置，并在2017年在CERN最终组装之前用H+离子进行测试。第二个应用是状态选择冷h2 +离子的光谱学，这将导致质子与电子质量比的新测定。BESCOOL项目将为未来的光谱应用和使用光原子和分子离子的基本测试提供新颖和通用的仪器。其中令人兴奋的前景是用于量子电动力学测试的高电荷离子的激光光谱学，量子逻辑时钟的应用，以及基本常数时间变化的研究。

In the last two decades, spectacular advances have been made in the quantum state control of ions confined in radiofrequency traps. Methods have been developed for laser cooling of the external motion down to the vibrational ground-state. Sympathetic cooling extended these techniques to many atomic and molecular species that cannot be directly laser cooled. Progress in ion transport allows performing each task in a separate, specifically optimized trap. As a result, trapped ions now represent one of the most advanced systems in the fields of quantum information and high precision measurements. This project aims at overcoming two important open questions of these techniques, which are still preventing investigation of highly interesting light ion species. Firstly, the above results were obtained with ions directly created inside the trap by electron impact or photo-ionization. However, many species such as antimatter ions, state-selected molecular ions, or highly charged ions are produced in external sources. We plan to develop a universal setup for transport, capture, and cooling of externally produced ions. The second challenge comes from the sympathetic cooling process, which becomes less efficient as the difference between the charge-to-mass (q/m) ratios of the laser-cooled and sympathetically cooled species increases, both for Doppler and ground-state cooling. We will experimentally investigate sympathetic cooling dynamics in the regime of high q/m differences, and develop cooling methods and trap geometries specifically adapted to this case. The first application is the GBAR project accepted by CERN in 2012; it concerns the first test of the equivalence principle with antimatter, through a free-fall experiment on neutral antihydrogen atoms. Both partners of the present project are among the 14 members of this international collaboration, and are involved in a key step: ground-state cooling of an antihydrogen positive ion in a Hbar+/Be+ ion pair. Our objective is to deliver the core of the GBAR experiment, complete setup for Hbar+ capture and cooling, tested with H+ ions before final assembly in 2017 at CERN. The second application is spectroscopy of state-selected cold H 2+ ions, that will result in a new determination of the proton-to-electron mass ratio.The BESCOOL project will provide novel and universal instrumentation for future spectroscopic applications and fundamental tests using light atomic and molecular ions. Among the exciting prospects is laser spectroscopy of highly charged ions for tests of quantum electrodynamics, quantum logic clock applications, and studies on time variations of fundamental constants.