|A>=a|0>+b|1> <A|A>=probability amp |<A|A>|^2=probability If the state is same, so <A|A>= a^2+b^2=1. then i find the probability and no interference term in it! so can i say <A|A>=|<A|A>|^2 and no square is needed? since if i square it become a^4+b^4=?? what wrong with it! and where should i place interference term?!