China has achieved a breakthrough in production of an ultra-pure form of silicon, a critical material needed to build silicon-based quantum computers, as Beijing accelerates its drive to cut reliance on foreign technology in strategic areas. State-owned nuclear giant China National Nuclear Corporation (CNNC) said on Monday that one of its research institutes had successfully mass-produced a high-purity silicon-28 isotope with an isotopic abundance above 99.99 per cent. The achievement marked...