What makes a quantum computer so different (and so much faster) than a conventional computer?

Answer 1

The quantum computer works using the quantum "fuzziness" of the universe rather than discrete yes/no answers like a conventional binary computer.

Here is a link on Wikipedia.

http://en.wikipedia.org/wiki/Quantum_computing

To simplify the explanation, what happens in the quantum computer is that all possible answers are evaluated, rather than actually calculating a single answer, and then probability is used to identify the "correct" (i.e. most likely) answer. The reason quantum computers are so fast is that they are massively parallel and perform all steps in the computation simultaneously rather than having to do it sequentially.