Onset of Chaos and Heating of Ion in Paul Trap: GPU-Accelerated MD Simulations*

In this work, we explore the onset of chaos and heating of a single ion in a Paul trap in the presence of a neutral bath. We use molecular dynamics simulations of a 174Yb+ ion starting at rest in the center of the Paul trap, and an atom launched directly toward the ion at a fixed initial kinetic energy of at least one microkelvin. We simulate several different trajectories, where each trajectory has the atom starting at a different initial spherical angle on a sphere centered at the ion. We use GPU acceleration to simulate 10 million trajectories in under 15 hours, each with more than 100,000 timesteps on average.

We observe the distribution of the scattering angle, number of bounces, ion distance traveled during the first bounce, complex lifetime, and momentum transfer. By repeating all the simulations with different parameters, we analyze how the trends in these observables depend on the depth of the atom-ion potential, the collision energy, and the mass and polarizability of the atom, either 7Li or 87Rb.

In this way, we systematically determine under which conditions chaos emerges, and how those conditions affect the initial amount of heating, in a Paul-trapped ion surrounded by a low density gas of atoms.