Si/SiGe spin qubits*

Electron spin qubits in silicon quantum dots are particularly promising candidates for the implementation of a large-scale quantum computer due to their small footprint. This compactness causes the noise to be correlated among neighboring qubits as was observed recently in an isotopically natural device [1]. In this work, we analyze the noise cross-correlation spectra of two interacting spin qubits in an isotopically purified ²⁸Si/SiGe device. The minimal effect of the nuclear spins in the material allows us to clearly observe the pure charge noise correlations between the fluctuating qubit energies and exchange interaction. With a simple microscopic model of electric fields shifting the position of the qubits within a magnetic gradient we can quantitatively reproduce the measured spectra. Finally, we distinguish the dominant coupling to two charge two-level systems in the vicinity of the qubits and approximately determine their location and characteristic switching times.

[1] J. Yoneda et al. Noise-correlation spectrum for a pair of spin qubits in silicon. Nat. Phys. (2023). https://doi.org/10.1038/s41567-023-02238-6