Hi there. Excuse that I write it all in standard text but I don't know how to write it otherwise. I'll get right to the question and try to see if I understand the theory from the answer. Suppose we have a system of two electrons, one spin up and one spin down in a system with 3 possible states, say 3 atomic levels. Suppose they are in a state [(up, down, 0)-(0,down,up)]/sqrt(2) (imagine it in Dirac notation ). How can I calculate the probability of finding spin down electron in the middle state, or the up electron in any of the other ones?