Scalable hyperfine qubit state detection via electron shelving in the \n2D5/2\n and \n2F7/2\n manifolds in \n171Yb+

Abstract

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 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 and achieve a 5.6× reduction in single-ion detection error on an avalanche photodiode to 1.8(2)× 10−3 in a 100 μs detection period, and a 4.3× error reduction on an electron multiplying CCD camera, with 7.7(2)× 10−3 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 F7/2 states populated after shelving. Finally, we examine the detection fidelity limit using the long-lived F7/2 state, achieving a further 300× and 12× reduction in error to 6(7)× 10−6 and 6.3(3)× 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 ultra-high fidelity detection in Yb.