  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.
