Spatial noise correlations beyond nearest neighbors in 28Si/Si-Ge spin qubits

We detect correlations in qubit-energy fluctuations of non-neighboring qubits defined in isotopically purified Si/Si-Ge quantum dots. At low frequencies (where the noise is strongest), the correlation coefficient reaches 10% for a next-nearest-neighbor qubit-pair separated by 200 nm. Correlations with the charge-sensor signal reach up to 70%, proving that the observed noise is of electrical origin. A simple theoretical model quantitatively reproduces the measurements and predicts a polynomial decay of correlations with interqubit distance. Our results quantify long-range correlations of noise in quantum-dot spin-qubit arrays, essential for their scalability and fault tolerance.

Automated summary

In this study, we detected correlations in qubit-energy fluctuations of non-neighboring qubits in isotopically purified Si/Si-Ge quantum dots. The correlation coefficient reached 10% for a next-nearest-neighbor qubit-pair separated by 200 nm at low frequencies where the noise is strongest. We also found correlations with the charge-sensor signal reaching up to 70%, proving the electrical origin of the observed noise. A simple theoretical model accurately reproduced the measurements and predicted a polynomial decay of correlations with interqubit distance. These results quantify the long-range correlations of noise in quantum-dot spin-qubit arrays, which are essential for scalability and fault tolerance.