and now, we need to factor numbers to generate cryptographic keys... (from "2020 Computing: Champing at the Bits" in Nature magazine's 2020 Future of Computing Web Focus. This kind of pedantic peeve aside, the web focus has some pretty interesting articles.
In fact, quantum computers are currently little more than two-trick wonders. In 1994, Peter Shor, now based at MIT, devised an algorithm that would allow quantum computers to factor numbers exponentially faster than conventional computers. Factorization is important in cryptography, where it is needed to make and break keys. And in 1996, Lov Grover, who is now at Lucent Technologies in Murray Hill, New Jersey, unveiled a quantum algorithm that can greatly speed up database searches.