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arXiv · 2409.05805

High-fidelity heralded quantum state preparation and measurement

A. S. Sotirova·J. D. Leppard·A. Vazquez-Brennan·S. M. Decoppet·F. Pokorny·M. Malinowski·C. J. Ballance
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Abstract

We present a novel protocol for high-fidelity qubit state preparation and measurement (SPAM) that combines standard SPAM methods with a series of in-sequence measurements to detect and remove errors. The protocol can be applied in any quantum system with a long-lived (metastable) level and a means to detect population outside of this level without coupling to it. We demonstrate the use of the protocol for three different qubit encodings in a single trapped $^{137}\mathrm{Ba}^+$ ion. For all three, we achieve the lowest reported SPAM infidelities of $7(4) \times 10^{-6}$ (optical qubit), $5(4) \times 10^{-6}$ (metastable-level qubit), and $8(4) \times 10^{-6}$ (ground-level qubit).

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A. S. Sotirova, J. D. Leppard, A. Vazquez-Brennan, S. M. Decoppet, F. Pokorny, M. Malinowski, C. J. Ballance. 2024-09-09. High-fidelity heralded quantum state preparation and measurement. https://arxiv.org/abs/2409.05805

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