Dressed-state relaxation in coupled qubits as a source of two-qubit gate errors

Ruixia Wang; Jiayu Ding; Chenlu Wang; Yujia Zhang; He Wang; Wuerkaixi Nuerbolati; Zhen Yang; Xuehui Liang; Weijie Sun; Haifeng Yu; Fei Yan

arXiv · 2601.11316

Dressed-state relaxation in coupled qubits as a source of two-qubit gate errors

Ruixia Wang·Jiayu Ding·Chenlu Wang·Yujia Zhang·He Wang·Wuerkaixi Nuerbolati·Zhen Yang·Xuehui Liang·Weijie Sun·Haifeng Yu·Fei Yan

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Abstract

Understanding error mechanisms in two-qubit gate operations is essential for building high-fidelity quantum processors. While prior studies predominantly treat dephasing noise as either Markovian or predominantly low-frequency, realistic qubit environments exhibit structured, frequency-dependent spectra. Here we demonstrate that noise at frequencies matching the dressed-state energy splitting--set by the inter-qubit coupling strength g--induces a distinct relaxation channel that degrades gate performance. Through combined theoretical analysis and experimental verification on superconducting qubits with engineered noise spectra, we show that two-qubit gate errors scale predictably with the noise power spectral density at frequency 2g, extending the concept of $T_{1\rho}$ relaxation to interacting systems. This frequency-selective relaxation mechanism, universal across platforms, enriches our understanding of decoherence pathways during gate operations. The same mechanism sets coherence limits for dual-rail or singlet-triplet encodings.

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Ruixia Wang, Jiayu Ding, Chenlu Wang, Yujia Zhang, He Wang, Wuerkaixi Nuerbolati, Zhen Yang, Xuehui Liang, Weijie Sun, Haifeng Yu, Fei Yan. 2026-01-16. Dressed-state relaxation in coupled qubits as a source of two-qubit gate errors. https://arxiv.org/abs/2601.11316

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