Scalable hyperfine qubit state detection via electron shelving in the 2D5/2 and 2F7/2 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 Yb-171(+) 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 Yb-171(+) and achieve a 5.6x reduction in single-ion detection error on an avalanche photodiode to 1.8(2) x 10(-3) in a 100 mu s detection period and a 4.3x error reduction on an electron multiplying CCD camera with 7.7(2) x 10(-3) error in 400 mu s. We further improve the characterization of a repump transition at 760 nm to enable a more rapid reset of the auxiliary F-2(7/2) states populated after shelving. Finally, we examine the detection fidelity limit using the long-lived F-2(7/2) state, achieving further 300x and 12x reductions in error to 6(7) x 10(-6) and 6.3(3) x 10(-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 ultrahigh-fidelity detection in Yb-171(+).

Automated summary

In this study, a detection routine based on electron shelving was demonstrated to significantly reduce single-ion detection error in Yb-171(+) ions. By improving the repump transition characterization and utilizing long-lived states, detection fidelity was further enhanced, paving the way for ultrahigh-fidelity detection in Yb-171(+).