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 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 state preparation and measurement-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.

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• Coherent control
• Quantum gates
• Qubits
• Ions
• Atom & ion cooling
• Atom & ion trapping & guiding
• Optical pumping