We look at this case in some detail. What can be said about what happens at time t 2 ? Well, it is possible that C 12 = C 23 = 1 , so that if the value of Q at t 1 is ± ± 1 , then it is also ± ± 1 for both times t 2 and t 3 . It is also quite possible that C 12 = C 23 = − − 1 , so that the value of Q at t 1 is flipped twice, and so has the same value at t 3 as it did at t 1 . So, we can have both Q ( t 1 ) and Q ( t 2 ) anti-correlated as long as we have Q ( t 2 ) and Q ( t 3 ) anti-correlated. Yet another possibility is that there is no correlation between Q ( t 1 ) and Q ( t 2 ) . That is, we could have C 12 = C 23 = 0 . So, although it is known that if Q = ± ± 1 at t 1 , it must also be ± ± 1 at t 3 ; the value at t 2 may as well be determined by the toss of a coin. We define K as K = C 12 + C 23 − − C 13 . In these three cases, we have K = 1 , − − 3 , − − 1 respectively.