Southwest Quantum Information and Technology

Coherent control of angular momentum states with a freely rotating Coulomb crystal

Presenting Author: Erik Urban, University of California Berkeley
Contributing Author(s): Neil Glikin, Sara Mouradian, Hartmut Haeffner

Rings of trapped ions provide unique access to experiments requiring periodic boundary conditions, spatial symmetry, and rotational modes. Here we demonstrate preparation and coherent control of rotational states in a two-ion ring. First, an in-plane quadrupole is used to accelerate the ions to a rotational velocity around 100 kHz. Then, the quadrupole is reduced to 0 which releases the ions into cylindrically symmetric harmonic potential in a high angular momentum state. In such a potential, the ion crystal acts as a 2D semirigid rotor with angular momentum eigenstates labeled by l. Finally, optical addressing of resolved rotational sidebands allows us to coherently drive population between angular momentum states l and l + dl where dl is between -4 and 4 with fidelities over 90%. Motional flop fidelities are increased by reducing the number of rotational eigenstates that are occupied. This is done through cooling the harmonic oscillator mode that eventually maps into the rotational mode before the ion crystal is spun up. Dynamically decoupled Ramsey experiments show coherence times of a few milliseconds, inversely correlated with dl.

(Session 5 : Sunday from 5:00pm - 7:00pm)