Characterizing charge-parity detection based on an offset-charge-tunable transmon qubit via randomized benchmarking

Quantum Physics [Submitted on 3 Apr 2026] Characterizing charge-parity detection based on an offset-charge-tunable transmon qubit via randomized benchmarking Yao-Yao Jiang, Tang Su, Yuxiang Liu, Yi-Ming Guo, Yidong Song, Yu-Long Li, Yanjie Zeng, Guang-Ming Xue, Wei-Jie Sun, Mei-Ling Li, Yi-Rong Jin, Junhua Wang, Xuegang Li, Hai-Feng Yu Superconducting qubits are compelling platforms for charge-parity detection and, due to their theoretical sensitivity on the meV energy scale, hold promise for rare event searches. In this work, we realize high-fidelity mapping of charge-parity states onto qubit states using an offset-charge-tunable transmon qubit and efficiently characterize the fidelity of the charge-parity detection via randomized benchmarking. Specifically, a gate control line is applied to control offset charge, allowing us to achieve the single-qubit gate fidelity up to 99.96%. We combine a net-zero-based pulse on the gate line with a spin-echo-based sequence to realize charge-parity mapping, achieving a fidelity of 99.37%. Then, we demonstrate continuous monitoring of the charge-parity state with over 93.4% fidelity at a 4-\mu s sampling interval. Finally, an error analysis of charge-parity detection is performed, and it is found that qubit readout is currently the largest source of error. We believe this work lays the foundation for future exploration of ultra-low energy particles. Comments: 11 pages and 9 figures Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2604.02809 [quant-ph]   (or arXiv:2604.02809v1 [quant-ph] for this version)   https://doi.org/10.48550/arXiv.2604.02809 Focus to learn more Submission history From: Xuegang Li [view email] [v1] Fri, 3 Apr 2026 07:19:47 UTC (8,004 KB) Access Paper: view license Current browse context: quant-ph < prev   |   next > new | recent | 2026-04 References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)