Editing PP (complexity) (section)

===PostBQP===
The quantum complexity class '''[[BQP]]''' is the class of problems solvable in [[polynomial time]] on a [[quantum Turing machine]]. By adding [[postselection]], a larger class called '''[[PostBQP]]''' is obtained. Informally, postselection gives the computer the following power: whenever some event (such as measuring a qubit in a certain state) has nonzero probability, you are allowed to assume that it takes place.<ref>{{cite web|url=http://www.scottaaronson.com/talks/postselect.ppt|title=The Amazing Power of Postselection|last=Aaronson|first=Scott|access-date=2009-07-27}}</ref> [[Scott Aaronson]] showed in 2004 that '''PostBQP''' is equal to '''PP'''.<ref name="PostBQP = PP"/><ref>{{cite web|url=http://weblog.fortnow.com/2004/01/complexity-class-of-week-pp-by-guest.html|title=Complexity Class of the Week: PP|last=Aaronson|first=Scott|date=2004-01-11|work=Computational Complexity Weblog|access-date=2008-05-02}}</ref> This reformulation of '''PP''' makes it easier to show certain results, such as that '''PP''' is closed under intersection (and hence, under union), that '''BQP''' is [[low (complexity)|low]] for '''PP''', and that '''[[QMA]]''' is included in '''PP'''.