Quantum computing isn't an easy subject to understand - let's be honest nothing quantum really makes sense. As Neils Bohr famously said: "If quantum mechanics hasn't profoundly shocked you, you haven't understood it yet." Fortunately two of my colleagues, Cris Calude and Alastair Abbott, do understand it and they've recently published a post on the Quantum for Quants website titled "Limits of Quantum Computing: A Sceptic's View". Highly recommended.
from The Universal Machine http://universal-machine.blogspot.com/