Rigetti stock isn't an investment, but a gamble.Rigetti Computing (RGTI 15.45%) surged ahead to close up 15.5% Wednesday after investment bank Cantor Fitzgerald initiated coverage of the quantum computing stock with an outperform rating (i.e., buy) and a $15 price target -- which, if correct, implies Rigetti stock could go up another 20% over the next 12 months. Quantum investing"Quantum computing is in its infancy," explains Cantor in a note covered on StreetInsider.com today, "but remains one of the most ...