Scalable hyperfine qubit state detection via electron shelving in the {}²D_5/2 and {}²F_7/2 manifolds in {}¹⁷¹Yb⁺

Qubits encoded in hyperfine states of trapped ions are ideal for quantum computation given their long lifetimes and low sensitivity to magnetic fields, yet they suffer from off-resonant scattering during detection often limiting their measurement fidelity. In {}¹⁷¹Yb⁺ this is exacerbated by a low fluorescence yield, which leads to a need for complex and expensive hardware - a problematic bottleneck especially when scaling up the number of qubits. We demonstrate a detection routine based on electron shelving to address this issue in {}¹⁷¹Yb⁺ and achieve a 5.6times reduction in single-ion detection error on an avalanche photodiode to 1.8(2)times10^-3 in a 100 μs detection period, and a 4.3times error reduction on an electron multiplying CCD camera, with 7.7(2)times10^-3 error in 400 μs. We further improve the characterization of a repump transition at 760 nm to enable a more rapid reset of the auxiliary ²F_7/2 states populated after shelving. Finally, we examine the detection fidelity limit using the long-lived ²F_7/2 state, achieving a further 300times and 12times reduction in error to 6(7)times10^-6 and 6.3(3)times10^-4 in 1 ms on the respective detectors. While shelving-rate limited in our setup, we suggest various techniques to realize this detection method at speeds compatible with quantum information processing, providing a pathway to ultra-high fidelity detection in {}¹⁷¹Yb⁺.