Existing decision tree building algorithm assumes that all topological relations occur with equal probability, but this situation is extremely rare in practice.

Mariantoni's group has used the new system to run an algorithm that is a kind of computational building block, called a Toffoli gate, which can be used to implement any conventional computer program.

Once people realized that they could "game" or manipulate the Google search algorithm by building masses of links from high PageRank websites, things had to change.