This quantum start-up has fallen substantially from its peak.It's generally not a good idea to buy stocks that have recently rallied based on hype. If the stock price growth doesn't reflect an improvement in fundamental metrics like profit or cash flow, it probably won't last very long. Investors in Rigetti Computing (RGTI +6.55%) learned this the hard way. Shares in the quantum computing start-up are down by an eye-popping 60% from their all-time high of $56 reached in October. That said, not much has chan ...