Towards a quantum toolbox for (anti-)proton precision measurements in Penning trap
Christian Ospelkaus (Univ. Hannover)

Laser cooling and state manipulation are key techniques in modern-day atomic and molecular physics experiments, both for fundamental tests and quantum technology applications. While laser cooling was initially demonstrated in a Penning trap, it has seen relatively little use in Penning-trap precision measurements. Present-day Penning trap mass and g-factor precision measurements are now at a level where laser cooling and control can provide critical advances both for measurement speed and accuracy. Yet most species of interest in Penning trap precision measurements do not possess suitable internal structure for laser manipulation. A particularly challenging and rewarding system is the (anti-)proton, which is being investigated by precision experiments within the BASE collaboration. In this and similar cases, hybrid approaches are highly desirable, where a laser-cooled ion with well-known internal structure is used to control the particle of interest. As part of BASE, we are setting up a cryogenic Penning trap apparatus for sympathetic cooling of single (anti-)protons by laser-cooled 9Be+ ions. We discuss how quantum logic spectroscopy, as first proposed by Heinzen and Wineland in 1990 and first used in the context of single-ion optical clocks, can be implemented in this system, and present both sympathetic cooling and state manipulation techniques. We discuss our most recent experimental results, demonstrating ground state cooling of the 9Be+ ion in the Penning trap as the key enabling step for any quantum logic based state manipulation of (anti-)protons.