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Homework Help: Quantum Spin up spin down with magnetic field

  1. Feb 15, 2012 #1
    There is an external magnetic field along the positive z direction B = (0,0, B) and the initial spin direction at time t0= 0 is specified by the direction cosines
    Ŝ0= (cos α0, cos β0, cos γ0)
    where α0, β0, γ0 are the angles between the initial spin and the x, y, z axes, respectively.
    This initial spin pointing in the direction Ŝ0 can be represented in terms of spin up and down states along z direction:
    ψ(α000 ) = A(α000 )α + B(α000β ) ,
    What are A and B?

    For the Psi= A alpha + B beta part alpha and beta represent the |+> and |-> z sates respectively.

    Hey everyone on this fine night,
    I really don't know where to start and was wondering if someone could give me a push in the right direction? Is this just asking what is the probability of it being up or down? I really can't get my foot out of the door on this :(
    Last edited: Feb 15, 2012
  2. jcsd
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