Source : Free On-Line Dictionary of Computing

quantum computer
     
         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.
     
        {Oxford University (http://eve.physics.ox.ac.uk/QChome.html)},
        {Stanford University (http://feynman.stanford.edu/qcomp/)}.
     
        A {quantum search algorithm
        (ftp://parcftp.xerox.com/pub/dynamics/quantum.html)} for
        {constraint satisfaction} problems exhibits the phase
        transition for {NP-complete} problems.
     
        (1997-02-11)