Magnetic Gradient Fluctuations from Quadrupolar <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msup><mml:mrow /><mml:mn>73</mml:mn></mml:msup><mml:mi>Ge</mml:mi></mml:math> in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Si</mml:mi></mml:math> / <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Si</mml:mi><mml:mi>Ge</mml:mi></mml:math> …

We study the time-fluctuating magnetic gradient noise mechanisms in pairs of Si/SiGe quantum dots using exchange echo spectroscopy. find through a combination spectral inversion and correspondence to theoretical modeling that quadrupolar precession $^{73}$Ge nuclei play key role spin-echo decay time $T_2$, with characteristic dependence on field width Si well. The peaks appear at fundamental first harmonic Larmor resonance, superimposed over $1/f$ due $^{29}$Si dipole-dipole dynamics, are dependent material epitaxy applied field. These results may inform needs dynamical decoupling when as qubits information processing devices.