Spin qubits in silicon-MOS (SiMOS) quantum dots have recently demonstrated compatibility with existing industry standard CMOS fabrication techniques. These devices have routinely achieved single- and two-qubit gate fidelities above 99% and demonstrated highly entangled two-qubit Bell states in isolated double quantum dot (DQD) unit cells, however coupling between unit cells has remained challenging. In this work, we present a two unit cell, four-qubit SiMOS processor with universal controllability and fully parallelised state initialisation and readout. We use this processor to generate maximally entangled three-qubit states, including the Greenberger-Horne-Zeilinger (GHZ) state, and certify multipartite entanglement through violation of the classical Mermin-witness bound. By using a fully symmetric dynamically decoupled gate sequence to create our entangled states, we are able to preserve the lifetime of the entanglement beyond T2∗, to a time limited instead by T2Hahn. These demonstrations pave a road to the scalable operation of larger SiMOS processors, and achieving high purity, long-lived multi-qubit entangled states in them.
@article{arxiv.2605.20781,
title = {Multi-Qubit Entanglement of Unit Cell Pairs in SiMOS},
author = {Cameron Jones and Jonathan Y. Huang and Santiago Serrano and MengKe Feng and Gerardo A. Paz-Silva and Tuomo Tanttu and Paul Steinacker and Fay E. Hudson and Wee Han Lim and Nikolay V. Abrosimov and Hans-Joachim Pohl and Michael L. W. Thewalt and Andrew S. Dzurak and Andre Saraiva and Arne Laucht and Chih Hwan Yang},
journal= {arXiv preprint arXiv:2605.20781},
year = {2026}
}