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arXiv · 2609.08598

Recovering Readout-Limited Fisher Information in Superconducting-Qubit Magnetometry with Squeezed Microwaves

M. -R. Yun·Y. -J. Qu·Zheng Shan·L. -L. Yan·Yu Jia·S. -L. Su
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Abstract

The performance of superconducting-qubit magnetometers depends not only on magnetic-field encoding during Ramsey interrogation, but also on how efficiently the encoded information is recovered during readout. Here we quantify how squeezed-microwave-assisted dispersive readout can recover magnetic-field information lost during qubit-state assignment. We develop an effective detected-mode framework linking projected quadrature noise, state-assignment error, and the classical Fisher information accessible from binary readout outcomes. A finite mismatch between the squeezed quadrature and the discrimination axis produces an optimal squeezing strength through the competition between squeezed and anti-squeezed fluctuations. For representative parameters, squeezed readout reduces the readout-limited magnetic-field sensitivity bound by $27.3\%$. This improvement arises from recovering information lost in the readout stage rather than from increasing the information encoded during Ramsey interrogation. These results may provide a practical route for mitigating measurement-stage information loss in superconducting quantum sensing.

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M. -R. Yun, Y. -J. Qu, Zheng Shan, L. -L. Yan, Yu Jia, S. -L. Su. 2026-09-08. Recovering Readout-Limited Fisher Information in Superconducting-Qubit Magnetometry with Squeezed Microwaves. https://arxiv.org/abs/2609.08598

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