Kapitza pendulums for many-body physics and precision measurement

The Kapitza pendulum, an inverted pendulum that is inherently unstable yet dynamically stabilized by high-frequency modulation of its pivot, is perhaps the most iconic example of dynamical stabilization of a single-particle system. Dynamical stabilization in the quantum many-body regime, however, remains largely unexplored, especially from an experimental perspective. In the first part of this talk, I will discuss experiments on ultracold atoms confined using time-periodic attractive and repulsive Gaussian potentials, the time average of which is zero [1] or positive. The resulting time-independent effective potential closely resembles that of the Kapitza pendulum. These experiments represent a step toward dynamical stabilization in synthetic many-body systems.
The Paul trap, widely used for the confinement of charged particles, probably represents the most notable Kapitza-pendulum-type device. In the second half of this talk, I will discuss precision measurements performed with laser cooled single 173Yb+ ions confined in a Paul trap. In particular, we have measured the hyperfine structures of the 2S1/2 and 2D3/2 states with a relative uncertainty below 10−8. Combined with state-of-the-art atomic structure calculations, these measurements provide updated insights into the deformation and magnetization distribution of the ytterbium nucleus [2], which is itself a quantum many-body system by its very nature.