DOI: 10.5281/zenodo.8004358
title: The source data for "Inductively shunted transmon: A superconducting qubit with flux noise insensitive plasmon states and a protected fluxon decay exceeding 3 hours"

description: The following folder contains all the raw data, analysis Mathematica notebook and ScQubits python codes used to generate the results in “Inductively shunted transmon: A superconducting qubit with flux noise insensitive plasmon states and a protected fluxon decay exceeding 3 hours” in nature communications. Please follow the instruction below for proper navigation through the data: Fig. 1 folder: Run “Color map of Matrix element Vs energy parameters” to generate “x.dat”, “y.dat”, ”M.dat”(respectively EJ/EL, EJ/EC and the matrix element of the first flux transition). <strong>Make sure to correct the address where these file should be saved</strong>. The mathematica notebook plots the dispersion in IST limit and the matrix element gray scale color map contours separately and the full image was constructed in illustrator later. The green dots on the dispersion plot represent the position of other qubits on the color map. Fig. 2&3 folder: The python file “paper figures” uses ScQubits to generate different studies in IST limit presented in Fig. 2&3 and generates the following files: Fig. 2a: “fluxonium.hdf5”: The spectrum of a typical fluxonium “fluxoniumME.hdf5”: The matrix element of all transition in “fluxonium.hdf5” Fig. 2d: “case1.hdf5”: The spectrum of fluxonium with EJ/EC=6.6 “ME1.hdf5”: The matrix element of transition in “case1.hdf5” “case2.hdf5”: The spectrum of fluxonium with EJ/EC=13 “ME2.hdf5”: The matrix element of transition in “case2.hdf5” . . “case6.hdf5”: The spectrum of fluxonium with EJ/EC=200 “ME6.hdf5”: The matrix element of transition in “case6.hdf5” “IST.hdf5”: The spectrum of the IST qubit “ISTME.hdf5”: The matrix element of transition in “IST.hdf5” “transmon.hdf5”: The spectrum of a transmon with the same EJ and EC as IST qubit Fig. 3a “Waveamp.hdf5”: The wave functions and eigenenergies of the IST qubit “WaveampT.hdf5”: The wave functions and eigenenergies of the transmon Fig. 3b: “ELcase1.hdf5”: The spectrum of IST qubit with EL=2 GHz “ELME1.hdf5”: The matrix element of transition in “ELcase1.hdf5” “ELcase2.hdf5”: The spectrum of IST qubit with EL=1.5 GHz “ELME2.hdf5”: The matrix element of transition in “ELcase2.hdf5” . . “ELcase6.hdf5”: The spectrum of IST qubit with EL=0.25 GHz “ELME6.hdf5”: The matrix element of transition in “ELcase6.hdf5” Fig. 3b inset: “WaveampEL.hdf5”contains the wave functions for El={2,1.5,1,0.75,0.5,0.25}GHz. Fig. 3c: “EC.hdf5” contains numerical simulation of an IST qubit with fixed EJ and Ec while EL is changing to calculate anharmonicity. The Mathematica notebook “Theory_figures” runs based on the files above and plot the result presented in the paper. Fig. 5 folder: Fig. 5a&b folder contains the raw data of spectroscopy of the IST qubit with different temperature and the Mathematica notebook “Tempsweeps_figa&b” simply plots the data. In the data set the I and Q quadrature as well as the amplitude and power of the signal coming back from cavity is provided. Fig. 5c folder contains several sweeps of both spectroscopy and resonator performed at fridge base temperature (7mK) labeled as “specge#.txt” and “Res_VNA_*.txt” respectively. The ScQubits python code “IST_Device” provides a fit for the data using the fit procedure explained in Supplementary Note 4 and generates the bare spectrum of the device saved in “Fit.h5”. The Mathematica notebook “spec_analysis” uses all spectroscopy data and the fit file to plot Fig. 5c. Fig. 6 folder: Contains all the raw data of T1 and T2 experiment at different flux positions across a flux quantum. The Mathematica notebook “T1&2” performs all the analysis presented in Fig. 6 for devices A, B and C. Fig. 7 folder: Fig. 7a: In this folder the we provide the raw data for fidelity experiment. The data is in the “*.mat” format and contains 40000 single shot I&Q bins collected with measurement band width of 2MHz and integration time of 500ns. The files names indicate whether the data was taken with qubit prepared in ground/excited state by having “_g_”/”_e_”. Following the state preparation condition, the measurement power at which the data was taken is indicated. The Mathematica notebook “fidelity_sweep” takes the data and extract the fidelities shown in Fig. 7a and the 2D histogram plots presented in Supplementary Figure 5d. Fig. 7b: The raw data for QND-ness experiment is presented in this folder. Each file contains 500 time traces of the two consecutive pulses applied to the resonator to study the non-QND effects of the IST qubit in high power. The Qubit preparation condition is apparent in the file name along with the power at which the measurement was performed. The Mathematica notebook “QND_ness” extracts the QND_ness and plots the results shown in Fig. 7b Fig. 8 folder: Fig. 8a: This folder contains the spectroscopy sweeps conditions by the fluxon state using a strong microwave pulse applied to the resonator. The Mathematica notebook “sweeps” plots the data. Fig. 8c: This folder contains the raw data for long fluxon decays collected using quantum machines (QM). In this experiment the fluxon excitation pulse was applied and repeated until a successful fluxon state is detected. Afterwards, the experiment enters monitoring stage where every 30s we check the fluxon state until a tunneling to fluxon ground state is detected. This event is logged and the QM repeats the fluxon excitation immediately followed by a monitoring stage and logging the time it took for tunneling to occur. The raw data of every 30 second monitoring stage is saved in files with “_raw_” in their labels. The files containing “_taus_” in their names have only the logged tunneling time events. The Mathematica notebook “qubit analysis” takes the data for three external flux bias and, by loading the “_taus_” files, reconstructs the quasi quantum jump traces and finally the decay traces presented in Fig. 8c.