Data supporting the publication: Coherence limitations of a Fourier-engineered cos(2φ) transmon qubit

The dataset includes measurements performed on devices operating in regimes, corresponding to the configurations discussed in the paper. Each regime is organized in a separate subfolder. In addition, the dataset contains resonator spectroscopy measurements. Data files are provided to reproduce the figures in the publication and to extract qubit parameters through fitting procedures.Measurements comprise continuous-wave and pulsed spectroscopy, as well as time-domain experiments used to determine coherence times T.All experimental data were acquired using the QCoDeS and Quantify Python packages. Each experiment folder contains raw and processed data stored in HDF5 format. Processed datasets, including extracted transition frequencies from spectroscopy measurements, are labeled with “extracted” in the filename.Data analysis scripts are available in the GitHub repository accompanying the publication, enabling reproduction of the results. A more detailed description of the dataset structure and contents is provided in the README file.