Utility-scale quantum computing requires the integration and operation of a large-scale qubit register. Semiconductor spin qubits are a primary candidate for this, due to the prospects of building integrated hybrid quantum-classical architectures. However, scaling spin-qubit systems while preserving performance and control has remained a challenge. Here, we demonstrate the operation of an 18-qubit array in germanium based on an extendable 2xN architecture. We achieve simultaneous initialization, control, and readout across the entire array, enabled by parallel operation of modular unit cells. Across the array, we achieve average and median single-qubit gate fidelities of 99.8% and 99.9%, respectively. Finally, we characterize the nearest-neighbor exchange couplings throughout the device and implement high-quality controlled-Z gates to generate a three-qubit Greenberger-Horne-Zeilinger (GHZ) state. These results demonstrate that spin-qubit arrays can be scaled while maintaining high-fidelity operation and establish a modular, extendable architecture for planar semiconductor quantum processors.
@article{arxiv.2604.01063,
title = {Simultaneous operation of an 18-qubit modular array in germanium},
author = {J. J. Dijkema and X. Zhang and A. Bardakas and D. Bouman and A. Cuzzocrea and D. van Driel and D. Girardi and L. E. A. Stehouwer and G. Scappucci and A. M. J. Zwerver and N. W. Hendrickx},
journal= {arXiv preprint arXiv:2604.01063},
year = {2026}
}