Coherent transfer of the transverse momentum of an optical vortex beam to the motion of a single trapped ion

TL;DR

This paper demonstrates the transfer of orbital angular momentum from a structured light vortex beam to the transverse motion of a single trapped ion, showing coherent spin-motion coupling in a quantum system.

Contribution

It introduces a method to coherently transfer transverse momentum from an optical vortex beam to a trapped ion's motion, a novel demonstration of spin-orbit interaction in quantum control.

Findings

Observed exchange of motional quanta in the transverse direction with vortex beams.

Measured an effective transverse Lamb-Dicke factor of approximately 0.0062.

Confirmed experimental results agree with theoretical predictions.

Abstract

We demonstrate the excitation, using a structured light beam carrying orbital angular momentum, of the center of mass motion of a single atom in the transverse direction to the beam's propagation. This interaction is achieved with a vortex beam carrying one unit of orbital angular momentum and one unit of spin/polarization angular momentum. Using a singly charged $^{40}$Ca$^+$ ion, cooled near the ground state of motion in the 3D harmonic potential of a Paul trap, we probe the narrow S$_{1/2}$ to D$_{5/2}$ transition near $729\,\mathrm{nm}$ on its motional sidebands to quantify the momentum transfer. Exchange of quanta in the perpendicular direction to the beam's wave vector $\mathbf{k}$ is observed in case of the vortex shaped beam, in strong contrast to the absence of this spin-motion coupling for the case of a Gaussian beam. We characterize the coherent interaction by an effective transverse Lamb-Dicke factor $\eta^\mathrm{exp}_{\perp}=0.0062(5)$ which is in agreement with our theoretical prediction $\eta^\mathrm{theo}_{\perp}=0.0057(1)$