Hi everybody! I'm trying to find the probability at time t of finding the state pointing in the positive x-direction of an initial system which points in the negative x-direction. I'm not sure if the result is correct, but I get the probability is sin^2(iwt). Can this be understood as the frequency w is a complex number? And what is complex frequency? Or if the frequency is not a complex number, how can I understand the result? Thanks for your help! ps: the problem is similar to the example Spin Precession in Sakurai book (page 75), but with complex number in the probability.