Shares of Xanadu Quantum Technologies (NASDAQ: XNDU) fell 10% this week, according to data from S&P Global Market Intelligence. The quantum stock had recently boomed after its merger with a special purpose acquisition company (SPAC), but has since fallen back to earth, almost back to its merger price. An insider sale this week further exacerbated losses. Here's why Xanadu Quantum sank, and whether now is a good time to buy this quantum stock. Missed Nvidia in 2009? This Rare Signal Is Flashing Again.