Quantum computing expert IonQ (IONQ -6.35%) is on a roll. The stock has gained a market-thumping 324% over the last year for reasons of mixed long-term importance. Quantum computers are starting to look useful, and there's a real business brewing there for the long term.But IonQ's investors may have jumped aboard its bandwagon too quickly, and the stock is now dangerously overvalued. IonQ stock is changing hands at 136 times the company's trailing revenues, and all of its profitability metrics are printed i ...