I think the chips were built with zero-spin silicon (ZS-Si) from Silex (SLX/SILXY): <a href="https://www.silex.com.au/silex-technology/silex-zs-si-production-for-quantum-computing" rel="nofollow">https://www.silex.com.au/silex-technology/silex-zs-si-produc...</a>