High-fidelity, adaptive qubit measurements through repetitive information transfer

Hume, D. B.; Rosenband, T.; Wineland, D. J.

High-fidelity, adaptive qubit measurements through repetitive information transfer

Authors

Hume, D. B.

Rosenband, T.

Wineland, D. J.

Description

Using two trapped ion species ($\rm{^{27}Al^+}$ and $\rm{^9Be^+}$) as primary and ancillary systems, we implement qubit measurements based on the repetitive transfer of information and quantum nondemolition detection. The repetition provides a natural mechanism for an adaptive measurement strategy, which leads to exponentially lower error rates compared to using a fixed number of detection cycles. For a single qubit we demonstrate 99.94 % measurement fidelity. We also demonstrate a technique for adaptively measuring multiple qubit states using a single ancilla, and apply the technique to spectroscopy of an optical clock transition.
Added Acknowledgements 4 pages, 4 figures