Color centers provide an optical interface to quantum registers based on electron and nuclear spin qubits in solids. The T center in silicon is an emerging spin-photon interface that combines telecom O-band optical transitions and an electron spin in a scalable photonics platform. In this work, we demonstrate the initialization, coherent control, and state readout of a three-qubit register based on the electron spin of a T center coupled to a hydrogen and a silicon nuclear spin. The spin register exhibits spin echo coherence times of 0.41(2)~ms for the electron spin, 112(12)~ms for the hydrogen nuclear spin, and 67(7)~ms for the silicon nuclear spin. We use nuclear-nuclear two-qubit gates to generate entanglement between the two nuclear spins with a fidelity of F=0.77(3) and a coherence time of T2∗=2.60(8)~ms. Our results show that a T center in silicon photonics can realize a multi-qubit register with an optical interface for quantum communication.
@article{arxiv.2504.15467,
title = {Entanglement of a nuclear spin qubit register in silicon photonics},
author = {Hanbin Song and Xueyue Zhang and Lukasz Komza and Niccolo Fiaschi and Yihuang Xiong and Yiyang Zhi and Scott Dhuey and Adam Schwartzberg and Thomas Schenkel and Geoffroy Hautier and Zi-Huai Zhang and Alp Sipahigil},
journal= {arXiv preprint arXiv:2504.15467},
year = {2025}
}