Charge-noise correlations in dense quantum-dot arrays

Fault‑tolerant quantum computing requires quantum‑error‑correction (QEC) protocols that encode high‑fidelity logical qubits from many noisy physical qubits. These protocols typically assume that physical errors are uncorrelated. However, this assumption may break down in solid‑state qubit platforms where qubits are arranged in extremely dense geometries. In gate-defined quantum‑dot spin qubits, localized charge defects or fluctuators can perturb multiple qubits simultaneously, potentially generating spatially correlated errors and undermining QEC performance [1].

This thesis aims to quantify the spatial correlation length scales of charge noise in large, densely packed quantum‑dot arrays. The work involves optimizing an existing millikelvin measurement setup for multi‑channel charge‑noise spectroscopy using quantum dots operated in transport (single‑electron transistors, SETs). By enabling parallel readout of multiple sites, the setup will allow direct measurement of correlation functions across the array. These experiments will be performed on a state‑of‑the‑art two‑dimensional quantum‑dot array fabricated using imec’s advanced spin‑qubit technology platform [2]. The results will provide valuable insight into the nature of correlated noise in semiconductor qubit processors and support the development of scalable, fault‑tolerant quantum computing architectures.

[1] Yoneda, J. et al. Noise-correlation spectrum for a pair of spin qubits in silicon. Nat. Phys. 19, 1793–1798 (2023).

[2] Steinacker, P. et al. Industry-compatible silicon spin-qubit unit cells exceeding 99% fidelity. Nature 646, 81–87 (2025).