Benchmarking the readout of a superconducting qubit for repeated measurements

• URL: http://arxiv.org/abs/2407.10934v1
• Date: Mon, 15 Jul 2024 17:34:13 GMT
• Title: Benchmarking the readout of a superconducting qubit for repeated measurements
• Authors: S. Hazra, W. Dai, T. Connolly, P. D. Kurilovich, Z. Wang, L. Frunzio, M. H. Devoret,
• Abstract summary: Readout of superconducting qubits faces a trade-off between measurement speed and unwanted back-action on the qubit. We show that such a characterization may significantly overlook readout-induced leakage errors. We apply this technique to characterize the dispersive readout of an intrinsically Purcell-protected qubit.
• Score: 1.710146779965826
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Readout of superconducting qubits faces a trade-off between measurement speed and unwanted back-action on the qubit caused by the readout drive, such as $T_1$ degradation and leakage out of the computational subspace. The readout is typically benchmarked by integrating the readout signal and choosing a binary threshold to extract the "readout fidelity". We show that such a characterization may significantly overlook readout-induced leakage errors. We introduce a method to quantitatively assess this error by repeatedly executing a composite operation -- a readout preceded by a randomized qubit-flip. We apply this technique to characterize the dispersive readout of an intrinsically Purcell-protected qubit. We report a binary readout fidelity of $99.63\%$ and quantum non-demolition (QND) fidelity exceeding $99.00\%$ which takes into account a leakage error rate of $0.12\pm0.03\%$, under a repetition rate of $(380 \rm{ns})^{-1}$ for the composite operation.

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