Two popular stocks among tech investors lately are Rigetti Computing (RGTI 0.86%), which makes quantum computing hardware and software, and the semiconductor company Nvidia (NVDA 4.11%). While Nvidia is a much more direct bet on the booming artificial intelligence (AI) market, Rigetti's quantum computing systems are integrated into some existing AI.Both stocks have soared, too, with Rigetti up 34% and Nvidia skyrocketing 342% over the past three years, compared to the S&P 500's 15% rise. But, which is the b ...