Kavli Affiliate: Menno Veldhorst
| First 5 Authors: Lucas E. A. Stehouwer, Cécile X. Yu, Barnaby van Straaten, Alberto Tosato, Valentin John
| Summary:
Disorder in the heterogeneous material stack of semiconductor spin qubit
systems introduces noise that compromises quantum information processing,
posing a challenge to coherently control large-scale quantum devices. Here, we
exploit low-disorder epitaxial strained quantum wells in Ge/SiGe
heterostructures grown on Ge wafers to comprehensively probe the noise
properties of complex micron-scale devices comprising of up to ten quantum dots
and four rf-charge sensors arranged in a two-dimensional array. We demonstrate
an average charge noise of $sqrt{S_{0}}=0.3(1)$
$mumathrm{eV}/sqrt{mathrm{Hz}}$ at 1 Hz across different locations on the
wafer, providing a benchmark for quantum confined holes. We then establish
hole-spin qubit control in these heterostructures and extend our investigation
from electrical to magnetic noise through spin echo measurements. Exploiting
dynamical decoupling sequences, we quantify the power spectral density
components arising from the hyperfine interaction with $^{73}$Ge spinful
isotopes and identify coherence modulations associated with the interaction
with the $^{29}$Si nuclear spin bath near the Ge quantum well. We estimate an
integrated hyperfine noise amplitude $sigma_f$ of 180(8) kHz from $^{73}$Ge
and of 47(5) kHz from $^{29}$Si, underscoring the need for full isotopic
purification of the qubit host environment.
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