Fig. 8: Characterization of low-frequency qubit noise spectra.
From: Tracking spin qubit frequency variations over 912 days
a A comparison of the PSDs extracted from the Ramsey data and the frequency scan data for qubits 1-6 in the linear device. The frequency calibration data is from period 10 as described in Fig. 4, which corresponds to the longest time period with a sufficient number of datapoints at a stable operating condition of gate voltage, magnetic field and temperature. The Ramsey data for qubits 1-3 was collected on 21/04/2023 and for qubits 4-6 on 29/06/2023. The solid red lines are fits to the Ramsey PSD data points to S0/fα, with S0 and α as fit parameters. The black dashed line is a guide to the eye showing a 1/f2 dependence. We note an unexpected change in slope of the PSD from 1/fα (with α ≈ 1) to 1/f2 at a transition frequency of approximately 10−4 Hz for all qubits. b Fitted values of α and Sf=1mHz of each PSD obtained from fits to the Ramsey data as in a. The DC gate voltage setting for each date is reported in Supplementary Section 3. The error bars (2σ) are extracted from the covariance matrix of the fit. The mixing chamber temperature at the time of data collection is shown at the top.
