A type of computer which uses the ability of
quantum systems, such as a collection of atoms, to be in many
different states at once. In theory, such superpositions
allow the computer to perform many different computations
simultaneously. This capability is combined with interference
among the states to produce answers to some problems, such as
factoring integers, much more rapidly than is possible with
conventional computers. In practice, such machines have not
yet been built due to their extreme sensitivity to noise.