High-fidelity entanglement of metastable trapped-ion qubits with integrated erasure conversion

TL;DR

This paper demonstrates high-fidelity control of metastable trapped-ion qubits with integrated erasure conversion, significantly reducing error rates and advancing the feasibility of fault-tolerant quantum computing.

Contribution

It introduces an erasure conversion scheme for metastable ion qubits and achieves near-perfect entanglement fidelity, enabling low-overhead fault-tolerant quantum computing.

Findings

94% detection of spontaneous Raman scattering errors

Bell state fidelity of 97.73% raw, 98.61% SPAM-corrected

99.16% fidelity when erasure errors are subtracted

Abstract

Today's most advanced ion trap quantum computers have significant overhead due to the need for dual-species operation. Looking ahead, logical qubit register sizes will be limited by the encoding rate needed to correct generic Pauli errors. We address both of these issues by establishing high-fidelity control of metastable qubits, a key component of \textit{omg} or dual-type architectures, which enables converting a significant fraction of gate errors to erasures. We first implement an erasure conversion scheme which enables detection of $\sim 94\%$ of spontaneous Raman scattering errors during logic gates and nearly all errors from qubit decay. Second, we perform a two-ion geometric phase gate using far-detuned (-44\,THz) stimulated Raman transitions to produce an entangled state with a raw Bell state fidelity of 97.73\% and a SPAM-corrected Bell state fidelity of 98.61\%. When subtracting erasure errors, this fidelity becomes 99.16\%. These results, along with projections based on our detailed error budget, demonstrate metastable trapped-ion qubits as a platform for low-overhead, fault-tolerant quantum computing.