  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 more than 13 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.
