Scalable quantum networks rely on optical connections between long-lived qubits to distribute entanglement. Tin vacancies in diamond have emerged as promising long-lived qubits, offering extended spin coherence times at liquid helium temperatures and spin-dependent, highly coherent optical transitions for effective photon-based communication. Connecting remote nodes requires quantum interference of indistinguishable photons, which is challenging in an inhomogeneous solid-state environment. Here, we demonstrate a two-node experiment with tin vacancies in diamond, which exhibit a resonant frequency distribution spanning approximately 8 GHz. To overcome the frequency mismatch, we tune the resonant frequencies of one node using the Stark effect. We achieve tunability up to 4 GHz while maintaining optical coherence. As a demonstration, we achieve detuning-dependent remote two-photon interference between separate nodes, obtaining 80(6)% interference visibility without postprocessing when the defects' optical transitions are tuned into resonance, and 63(8)% with detuning up to 20 times their natural linewidths. These results highlight the potential of tin-vacancy centres in diamond for establishing robust optical links between remote quantum registers.
@article{arxiv.2412.17539,
title = {Two-Photon Interference of Photons from Remote Tin-Vacancy Centers in Diamond},
author = {Vladislav Bushmakin and Oliver von Berg and Colin Sauerzapf and Sreehari Jayaram and Andrej Denisenko and Cristina Tarín and Jens Anders and Vadim Vorobyov and Ilja Gerhardt and Di Liu and Jörg Wrachtrup},
journal= {arXiv preprint arXiv:2412.17539},
year = {2025}
}