Identify additional hyperfine-interaction contributions to FM-qubit noise

Determine whether hyperfine-interaction effects beyond the expected $^{73}$Ge isotope contribution are present in the flopping-mode qubit’s noise power spectral density.

Background

The supplementary noise-spectrum analysis compares power spectral densities measured at the detuning sweet spot and away from it. The authors identify an expected 73^{73}Ge isotope contribution at approximately 7.4 kHz for the selected magnetic field, but the measured spectrum may contain additional features or effects that are not accounted for by this explanation.

The unresolved issue is relevant because the low-frequency noise limits the interpretation of the flopping-mode qubit’s coherence. Establishing whether other hyperfine-related mechanisms contribute would help distinguish magnetic noise from charge noise and clarify the origin of the observed spectral behavior.

References

However, we cannot rule out other effects of hyperfine interactions .

— Coherent and ultra-low-power EDSR with a flopping-mode spin qubit in germanium  (2609.20775 - Orekhov et al., 17 Sep 2026) in Supplementary Materials, Section “Flopping-mode qubit noise spectrum”