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Homework Help: Why is <n|n-2> = 0?

  1. Jan 23, 2015 #1
    1. The problem statement, all variables and given/known data

    This is not really homework. I'm just studying and came across this question. So, I'm not sure if I should post this question here on one of the physics sections.

    On computing ##<n|\hat{a}^2|n>##, one arrives at ##\sqrt{n}*\sqrt{n-1}<n|n-2>=0## because ##<n|n-2>=0##

    Now, why is that so?
     
  2. jcsd
  3. Jan 23, 2015 #2
    Isn't that just because the two Fock states are orthogonal?
     
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