As a case in point, Warren Buffett, Bill Ackman, and David Tepper have portfolios that look very different. But there's one stock -- and only one stock -- that all three of these billionaires own.

Buffett doesn't have any quantum computing stocks in Berkshire Hathaway's portfolio. All three companies are investing heavily in quantum computing, but there are better reasons to buy the stocks. Theoretical physicist Richard Feynman once said,