Pair Correlations in Atomic Bose Gases

对关联在相互作用的量子气体物理学中起着核心作用。在玻色和费米气体中，它们可以在费什巴赫共振的帮助下在许多数量级上变化。这种控制在当前的研究中以各种方式使用，使原子量子气体领域对于更深入地理解量子多体系统非常富有成果。到目前为止，对关联只能通过与它们相关的增加的非弹性散射损失来观察。这种方法非常耗时，因为对于每个数据点，必须运行几十秒的完整实验周期。因此，记录有意义的光谱需要几天到几周的时间。去年，我们开发了一种方法，克服了这些问题，使我们能够在不破坏原子量子气体的情况下，以小于100纳秒的时间分辨率原位观察对相关性。在本建议中，我们希望进一步发展该方法，并将其应用于两个基本问题。第一个问题涉及酉玻色气体。酉玻色气体是在小距离处具有最大对关联的量子气体。它们是普遍的多体系统，其性质仅取决于原子的质量和粒子密度。由于其基本的重要性，它们目前是密集的实验和理论研究的主题。我们计划用我们的方法来研究幺正玻色气体的动力学性质。为此，散射长度被周期性地调制，并且在原位以高时间分辨率检测在离子信号中直接可观察到的对相关性的变化。在第二子项目中，我们计划使用我们的方法来检测Efimov三聚体。在我们的Tübingen锂-铷混合物中，我们研究了束缚异质结Efimov三聚体态。在这里，我们以前也依赖于对三体损失的极其耗时和嘈杂的观察。由一个轻原子（锂）和两个重原子（铷）组成的Efimov态可以通过消除轻原子的快速动力学来归因于两体问题。这导致了两个重原子之间的额外电势。由此产生的重原子对相关性的变化应该可以在原位和真实的时间内在离子信号中观察到。

Pair correlations play a central role in the physics of interacting quantum gases. In atomic Bose and Fermi gases they can be varied over many orders of magnitude with the help of Feshbach resonances. This control is used in a variety of ways in current research and makes the field of atomic quantum gases extremely fruitful for a deeper understanding of quantum many-body systems.Until now, pair correlations could only be observed via the increased inelastic scattering losses associated with them. This method is very time-consuming, since for each data point a complete experimental cycle of several tens of seconds must be run through. The recording of meaningful spectra therefore requires several days to weeks. Last year, we developed a method that overcomes these problems and allows us to observe pair correlations in situ with a time resolution of less than 100 nanoseconds without destroying the atomic quantum gas. With the present proposal we want to further develop the method and apply it to two fundamental questions. The first issue concerns unitary Bose gases. Unitary Bose gases are quantum gases with maximum pair correlation at small distances. They are universal many-body systems whose properties depend only on the mass of the atoms and the particle density. Due to their fundamental importance, they are currently the subject of intensive experimental and theoretical research. We plan to use our method to study the dynamic properties of unitary Bose gases. For this purpose, the scattering length is periodically modulated and the change of the pair correlation observable directly in the ion signal is detected in situ and with high time resolution. In a second subproject we plan to use our method to detect Efimov trimers. In our Tübingen lithium-rubidium mixture we have investigated bound heteronuclear Efimov trimer states. Here, too, we were previously dependent on the extremely time-consuming and noisy observation of three-body losses. Efimov states consisting of one light atom (lithium) and two heavy atoms (rubidium) can be attributed to a two-body problem by adiabatically eliminating the fast dynamics of the light atom. This leads to an additional potential between the two heavy atoms. The resulting change in the pair correlation of the heavy atoms should be observable in the ion signal in situ and in real time.