Operating a bistable qubit

• URL: http://arxiv.org/abs/2605.03187v1
• Date: Mon, 04 May 2026 22:06:43 GMT
• Title: Operating a bistable qubit
• Abstract summary: Parasitic two-level-system defects limit the stability and performance of quantum processors.<n>We show an adaptive protocol for operating a bistable qubit with high fidelity.<n>Our approach may enable the operation of large future qubit arrays suffering from few remaining, discrete instabilities.
• Score: 23.393046082340447
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Parasitic two-level-system (TLS) defects limit the stability and performance of solid-state quantum processors. Their interaction with a qubit can cause discrete, stochastic shifts of the qubit frequency, making the qubit bistable. We experimentally demonstrate an adaptive protocol for operating a bistable qubit with high fidelity using a classical controller powered by a field-programmable gate array (FPGA). Our "1-bit feedback" protocol estimates the qubit's bistable frequency from only one single-shot measurement, reaching the information limit set by the qubit's intrinsic entropy. We validate the protocol in a superconducting qubit by suppressing TLS-induced Ramsey beating, and deploy it to stabilize gate fidelities over time with approximately 136 kHz estimation bandwidth and a 77% error reduction. Our approach provides a simple, yet fundamentally efficient strategy for mitigating dephasing errors induced by strongly coupled TLS defects, and may enable the operation of large future qubit arrays suffering from few remaining, discrete instabilities.

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