1. The problem statement, all variables and given/known data Hi all. Lets say that we are looking at an operator Q, and two eigenstates given by |1> and |2>. The eigenstates |1> and |2> are not eigenstates of Q, but of some other operator H. My question: Is <1|Q|1>, <1|Q|2>, <2|Q|1> and <2|Q|2> independent of the basis used as long as Q, |1> and |2> are given in the same basis? Thanks in advance. Sincerely, Niles.