阿摩線上測驗
題組內容
15. (20 pts) Consider the spin state of a proton. Recall that the spin operators are
where i =
. Suppose that a static external magnetic field is applied along the y direction, so that the hamiltonian is 
where B is the magnetic field strength, and
is a real constant. Denote the spin up state a and the spin down stateβ as
(e)6 pts) Calculate the vector
represents the expectation value of the operator
at the time t. Plot the three components of this vector as functions of time.