Origin of 1/f charge noise in silicon spin qubits
In plain words
Spin qubits in silicon are disturbed by slowly fluctuating electric fields from charges hopping in nearby materials. Where those charges are and why their spectrum follows 1/f is not known.
Precise statement
In Si/SiGe and Si-MOS quantum-dot qubits, charge noise with $S_E(1\,\mathrm{Hz})^{1/2}$ of order $0.1-1\,\text{micro-eV}/\mathrm{Hz}^{1/2}$ and spectral exponent near 1 limits dephasing and two-qubit gate fidelity, with temperature and frequency dependence that vary between devices. Identify the fluctuator ensemble (defects in gate oxides, in the SiGe barrier, or at interfaces) and its location, using noise correlations between neighboring dots and dependence on the gate stack.
What would settle it
Spatially resolved noise correlations between neighboring dots plus heterostructure changes that alter the noise amplitude as a specific defect model predicts.