Spontaneous Raman scattering out of a metastable atomic qubit

TL;DR

This paper measures spontaneous Raman scattering rates in a metastable atomic qubit, providing insights into error rates for quantum computing with trapped ions and demonstrating the potential for very low infidelity gates.

Contribution

It presents the first measurement of Raman scattering rates from a metastable $D_{5/2}$ qubit in a trapped $^{40}$Ca$^+$ ion, supporting error rate calculations for quantum gates.

Findings

Measured Raman scattering rates support error rate estimates below 10^{-4}

Demonstrated that high-fidelity quantum gates are feasible with metastable qubits

Provided experimental data to optimize laser detuning for minimal scattering

Abstract

Metastable qubits in atomic systems can enable large-scale quantum computing by simplifying hardware requirements and adding efficient erasure conversion to the pre-existing toolbox of high-fidelity laser-based control. For trapped atomic ions, the fundamental error floor of this control is given by spontaneous Raman and Rayleigh scattering from short-lived excited states. We measure spontaneous Raman scattering rates out of a metastable $D_{5/2}$ qubit manifold of a single trapped $^{40}$Ca$^+$ ion illuminated by 976 nm light that is -44 THz detuned from the dipole-allowed transition to the $P_{3/2}$ manifold. This supports the calculation of error rates from both types of scattering during one- and two-qubit gates on this platform, thus demonstrating that infidelities $<10^{-4}$ are possible.