From: jos.bergervoet@nxp.com   
      
   Consider a Stern-Gerlach device using a field in the z-direction.   
      
   Entering is a single-electron Gaussian wave packet with spin   
     Psi(x) ( |u> + |d> ) / sqrt(2)   
   where the initial spin is clearly in x-direction.   
      
   We know the apparatus will split the trajectory of the components   
   and due to the non-uniform grading of the field two separate wave   
   packets will come out, moving in slightly different directions.   
      
   But before the separation is complete, isn't there fast precession   
   of the spin around the z-axis? And then wouldn't the electron radiate   
   energy, so fall down to the energy level of the |d> spin which in   
   the field is lower than the |u> spin?   
      
   So my question is: do we expect more down-spin to come out than up-   
   spin? (When the input components both have exactly equal amplitude,   
   I mean!) Or is there a reason for this mechanism to be insignificant?   
      
   --   
   Jos   
      
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