SAN FRANCISCO :Quantum computing startup PsiQuantum is raising at least $750 million at a $6 billion pre-money valuation, according to two people familiar with the matter. BlackRock is leading the fundraising effort, which has not yet been completed, one of the people said. Unlike some quantum computing startups using exotic materials, PsiQuantum is aiming to modify traditional manufacturing techniques from the semiconductor industry. The company uses existing photonics technology - the same