Charge-noise spectroscopy of Si/SiGe quantum dots via dynamically-decoupled exchange oscillations

Electron spins in silicon quantum dots are promising qubits due to their long coherence times, scalable fabrication, and potential for all-electrical control. However, charge noise in the host semiconductor presents a major obstacle to achieving high-fidelity single- and two-qubit gates in these devices. In this work, we measure the charge-noise spectrum of a Si/SiGe singlet-triplet qubit over nearly 12 decades in frequency using a combination of methods, including dynamically-decoupled exchange oscillations with up to 512 {\pi} pulses during the qubit evolution. The charge noise is colored across the entire frequency range of our measurements, although the spectral exponent changes with frequency. Moreover, the charge-noise spectrum inferred from conductance measurements of a proximal sensor quantum dot agrees with that inferred from coherent oscillations of the singlet-triplet qubit, suggesting that simple transport measurements can accurately characterize the charge noise over a wide frequency range in Si/SiGe quantum dots.

Comment: Main: 10 pg, 5 fig. Supp: 15 pg, 11 fig. Supp Notes: Hadamard gate calibration, t_{meas}, dBz and J_{min}, Charge-noise v temp. Supp Figs: Readout, FID, CPMG filter function, Echo analysis, Noise extraction error from CPMG, Samp rate in three-day FID, Charge-noise correlations, Charge-sensor spectra, Automated Hadamard calibration, dBz v B_{ext}, Echo v temp. Supp Tables: Lever arms, t_{meas}