Dressed-state relaxation in coupled qubits as a source of two-qubit gate errors
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 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.
Keywords
Cite
@article{arxiv.2601.11316,
title = {Dressed-state relaxation in coupled qubits as a source of two-qubit gate errors},
author = {Ruixia Wang and Jiayu Ding and Chenlu Wang and Yujia Zhang and He Wang and Wuerkaixi Nuerbolati and Zhen Yang and Xuehui Liang and Weijie Sun and Haifeng Yu and Fei Yan},
journal= {arXiv preprint arXiv:2601.11316},
year = {2026}
}