Moore's Law sates that computer power doubles every 18 months. This law is held for 50 years or so, but physicists ad computer engineers are facing now a new reality: Moore's law will expire in the next 10 years. Computer engineers must come up with totally new solutions to engineer more powerful computers, because silicon computers cannot go any further.
Quantum computers is one possibility. I posted once a BLOG entry explaining how quantum computers will probably work. It seems though that there are great difficulties in stability and reliability of quantum computers. Michio Kaku believes that molecular computers will be the first breakthrough, since molecular transistors already exist!