In Clone Wars, Quantum Computers Need Not Apply

Abstract

If bloodthirsty legions of identical self-replicating robots bent on the destruction of humanity haunt your dreams, rest easy. Science has proven that they can't exist—at least not if they have quantum brains. In a paper submitted to Physical Review Letters, two physicists have shown that it is impossible to build a quantum “universal constructor”—a quantum computer that has the ability to spawn perfect copies of itself.