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arXiv · 2009.08079

Magnetic Gradient Fluctuations from Quadrupolar $^{73}$Ge in Si/SiGe Exchange-Only Qubits

J. Kerckhoff·B. Sun·B. H. Fong·C. Jones·A. A. Kiselev·D. W. Barnes·R. S. Noah·E. Acuna·M. Akmal·S. D. Ha·J. A. Wright·B. J. Thomas·C. A. C. Jackson·L. F. Edge·K. Eng·R. S. Ross·T. D. Ladd
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Abstract

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

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J. Kerckhoff, B. Sun, B. H. Fong, C. Jones, A. A. Kiselev, D. W. Barnes, R. S. Noah, E. Acuna, M. Akmal, S. D. Ha, J. A. Wright, B. J. Thomas, C. A. C. Jackson, L. F. Edge, K. Eng, R. S. Ross, T. D. Ladd. 2020-09-17. Magnetic Gradient Fluctuations from Quadrupolar $^{73}$Ge in Si/SiGe Exchange-Only Qubits. https://doi.org/10.1103/prxquantum.2.010347

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