Rydberg and ion impurities in ultracold quantum matter

• Applicant: Professor Dr. Tilman Pfau
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2016 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 316184878

We propose to implant single Rydberg atoms into bosonic and fermionic quantum gases at unprecedented spatial and temporal control with the aim to study quantum scattering and Transport phenomena in hybrid ion-atom systems and to devise new ways for probing quantum correlations in interacting quantum matter. These goals will be tackled in a quantum gas apparatus developed during the first funding period of the GiRyd program. The setup is conceivedfor simultaneous production of degenerate gases of Li and Rb. The apparatus incorporates an ion microscope for spatially and temporally resolved read-out of single ionized Rydberg atoms, serving as an integral part for the project objectives proposed here. Importantly,Rydberg blockade is used in our system to single out one isolated Rydberg impurity to start with. This isolated impurity forms the starting point for the following experiments. First, we will study collisions in hybrid ion-atom systems with the central goal to observe the so farunexplored regime of ion-atom quantum scattering at energies where only few partial waves contribute. Li appears as a prime candidate to reach the pure s-wave scattering regime due to its light mass. We intend to engineer controlled two-body collisions starting from preformed ultralong-range Rydberg molecules, with the goal to detect the collision process spatially resolved and at the level of a single scattering event. We will then go further and investigate three-body collisions in the hybrid system, which constitutes a major aspect forstudies of a stable ion impurity in a quantum many-body environment. The understanding of the few-body scattering physics finally forms the basis to investigate ion impurities immersed in quantum degenerate gases at high spatial resolution with particular focus on transportproperties. For all these studies, Rydberg atoms form the essential precursor for creating and controlling single ultra-low energy ions. The second part of the project aims to establish ultralong-range Rydberg molecules as a new tool for probing spatial correlations in a quantummany-body system. Building on our previous studies of single Rydberg atoms interacting with a Bose-Einstein condensate, we will extend these experiments to the case of degenerate Fermions. Given the compatible length scales of Fermi correlations and the Rydberg molecule size, we expect signatures of local pair correlations in the molecular excitation spectra. The Rydberg molecule’s tunable size may further offer a rather unique approach to probe spatial correlationfunctions.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1929: Giant Interactions in Rydberg Systems (GiRyd)
• Major Instrumentation: frequency doubling stage
• Instrumentation Group: 5770 Lichtmodulatoren, Elektrooptik, Magnetooptik
• Co-Investigator: Florian Meinert, Ph.D.