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arXiv:2511.10978 · PRX Quantum

Maximizing the nondemolition nature of a quantum measurement via an adaptive readout protocol

Arjen Vaartjes, Rocky Yue Su, Laura A. O'Neill, Paul Steinacker, Gauri Goenka, Mark R. van Blankenstein, Xi Yu, Benjamin Wilhelm, Alexander M. Jakob, Fay E. Hudson, Kohei M. Itoh, Chih Hwan Yang, Andrew S. Dzurak, David N. Jamieson, Martin Nurizzo, Danielle Holmes, Arne Laucht, Andrea Morello

quant-phcond-mat.mes-hallSubmitted Nov 14, 2025• Announced Nov 17, 2025• 1 citation
v1 · Nov 14, 2025v2 · Nov 21, 2025
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Abstract

Quantum error correction (QEC) requires non-invasive measurements for fault tolerant quantum computing. Deviations from ideal quantum non-demolition (QND) measurements can disturb the encoded information. To address this challenge, we develop a readout protocol for a $D-$dimensional system that, after a single positive outcome, switches to probing only the $D{-}1$ remaining subspace. This adaptive switching strategy minimizes measurement-induced errors by relying on negative-result measurement results that do not perturb the Hamiltonian. We apply the protocol on an 8-dimensional $^{123}{\rm Sb}$ nuclear qudit in silicon, and achieve an increase in the readout fidelity from $(98.93\pm0.07)\%$ to $(99.61\pm0.04)\%$, while reducing threefold the overall readout time. To highlight the broader relevance of measurement-induced errors, we study a 10-dimensional $^{73}{\rm Ge}$ nuclear spin read out through Pauli spin blockade, revealing nuclear spin flips arising from hyperfine and quadrupole interactions. These results unveil the effect of non-ideal QND readout across diverse platforms, and introduce an efficient readout protocol that can be implemented with minimal FPGA logic on existing hardware.

Journal reference
PRX Quantum 7, 020330 (2026)
DOI
10.1103/jtn1-wzyl
Comments
Main text: 10 pages, 5 figures. Supplementary Material: 7 pages, 5 figures

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