Trapped Ion Quantum Computing using Optical Tweezers and the Magnus Effect

TL;DR

This paper proposes a novel method for implementing quantum logic gates in trapped ion systems using optical tweezers and the Magnus effect, enabling high-fidelity operations without ground state cooling or Lamb-Dicke approximation.

Contribution

It introduces a new gate scheme utilizing polarization gradients and optical tweezers that simplifies setup and improves robustness in trapped ion quantum computing.

Findings

Gate fidelity exceeds 99.998% with minimal pointing errors

No need for ground state cooling or Lamb-Dicke approximation

Compatible with clock state qubits and single-beam setup

Abstract

We consider the implementation of quantum logic gates in trapped ions using tightly focused optical tweezers. Strong polarization gradients near the tweezer focus lead to qubit-state dependent forces on the ion. We show that these may be used to implement quantum logic gates on pairs of ion qubits in a crystal. The qubit-state dependent forces generated by this effect live on the plane perpendicular to the direction of propagation of the laser beams opening new ways of coupling to motional modes of an ion crystal. The proposed gate does not require ground state cooling of the ions and does not rely on the Lamb-Dicke approximation, although the waist of the tightly focused beam needs to be comparable with its wavelength in order to achieve the needed field curvature. Furthermore, the gate can be performed on both ground state and magnetic field insensitive clock state qubits without the need for counter-propagating laser fields. This simplifies the setup and eliminates errors due to phase instabilities between the gate laser beams. Finally, we show that imperfections in the gate execution, in particular pointing errors $<30$ nm in the tweezers reduce the gate fidelity from $\mathcal F\gtrsim 0.99998$ to $\gtrsim 0.999$.