Photon scattering errors during stimulated Raman transitions in trapped-ion qubits

TL;DR

This paper refines models of photon scattering errors in trapped-ion quantum gates, showing that previous overestimations can be corrected, and that low error rates are achievable with proper detuning.

Contribution

The authors develop an improved model accounting for previously neglected effects, reducing estimated photon scattering errors in Raman-driven trapped-ion quantum gates.

Findings

Previous models overestimated scattering errors by neglecting key factors.

Corrected models show no fundamental error limit for ground state qubits with red-detuned lasers.

Metastable D_{5/2} qubits can achieve errors below 10^{-4}.

Abstract

We study photon scattering errors in stimulated Raman driven quantum logic gates. For certain parameter regimes, we find that previous, simplified models of the process significantly overestimate the gate error rate due to photon scattering. This overestimate is shown to be due to previous models neglecting the detuning dependence of the scattered photon frequency and Lamb-Dicke parameter, a second scattering process, interference effects on scattering rates to metastable manifolds, and the counter-rotating contribution to the Raman transition rate. The resulting improved model shows that there is no fundamental limit on gate error due to photon scattering for electronic ground state qubits in commonly-used trapped-ion species when the Raman laser beams are red detuned from the main optical transition. Additionally, photon scattering errors are studied for qubits encoded in metastable $D_{5/2}$ manifold, showing that gate errors below $10^{-4}$ are achievable for all commonly-used trapped ions.