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arXiv · 0802.1684

High-fidelity readout of trapped-ion qubits

A. Myerson·D. Szwer·S. Webster·D. Allcock·M. Curtis·G. Imreh·J. Sherman·D. Stacey·A. Steane·D. Lucas
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Abstract

We demonstrate single-shot qubit readout with fidelity sufficient for fault-tolerant quantum computation, for two types of qubit stored in single trapped calcium ions. For an optical qubit stored in the (4S_1/2, 3D_5/2) levels of 40Ca+ we achieve 99.991(1)% average readout fidelity in one million trials, using time-resolved photon counting. An adaptive measurement technique allows 99.99% fidelity to be reached in 145us average detection time. For a hyperfine qubit stored in the long-lived 4S_1/2 (F=3, F=4) sub-levels of 43Ca+ we propose and implement a simple and robust optical pumping scheme to transfer the hyperfine qubit to the optical qubit, capable of a theoretical fidelity 99.95% in 10us. Experimentally we achieve 99.77(3)% net readout fidelity, inferring at least 99.87(4)% fidelity for the transfer operation.

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A. Myerson, D. Szwer, S. Webster, D. Allcock, M. Curtis, G. Imreh, J. Sherman, D. Stacey, A. Steane, D. Lucas. 2008-04-22. High-fidelity readout of trapped-ion qubits. https://doi.org/10.1103/physrevlett.100.200502

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