What is a Quantum Computer?

[Kire]

In a quantum computer, the fundamental unit of information (called a quantum bit or qubit), is not binary but rather more quaternary in nature. This qubit property arises as a direct consequence of its adherence to the laws of quantum mechanics which differ radically from the laws of classical physics. A qubit can exist not only in a state corresponding to the logical state 0 or 1 as in a classical bit, but also in states corresponding to a blend or superposition of these classical states. In other words, a qubit can exist as a zero, a one, or simultaneously as both 0 and 1, with a numerical coefficient representing the probability for each state. This may seem counterintuitive because everyday phenomenon are governed by classical physics, not quantum mechanics -- which takes over at the atomic level. This rather difficult concept is perhaps best explained through an experiment. Consider figure a below:

More: http://www.cs.caltech.edu/~westside/quantum-intro.html#qc

[SKKY]

1. It's a really, really, super-fast computer that will make one hell of...

...a Doom server! Check out "The Code Book". There's a nice section in there about Quantum Computing as it pertains to cryptography.