Description
Speaker:
Prof Moonjoo Lee
Pohang University of Science and Technology (POSTECH)
Abstract:
We begin by discussing our experimental study of nonlinear mechanical oscillations in trapped ions. Specifically, we demonstrate the tunability of the Duffing nonlinearity of the ion oscillator, allowing it to transition from the softening to the hardening regime. Furthermore, when the ion velocity exceeds a critical threshold, we observe the formation of a phononic frequency comb in the ion’s motional spectrum. By analyzing the experimental data, we reconstruct the phase-space dynamics and the Poincaré map of the ion motion.
The next part focuses on theoretical work with non-Hermitian dynamics arising when a single ion or atom is coupled to an optical resonator. When the strength of coherent interaction balances the dissipation rate, second- or third-order exceptional points can emerge in the system. In addition, we show that introducing a nanotip into the mode of a Fabry-Perot-type resonator enables controlled tuning of the dissipation rate. This capability allows us to generate an exceptional line and realize a dissipation-induced topological transition, in which the exceptional point can be tuned solely through the control of dissipation.
Finally, we present our experiments with a chain of approximately 100 ions. The ions can be individually manipulated and cooled close to their motional ground state. We discuss experiments on phonon hopping in the ion chain, as well as measurements of both the local and global density of states.