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Homework Help: Quantum Operators - Eigenvalues & states

  1. Jan 11, 2012 #1
    1. The problem statement, all variables and given/known data

    an operator for a system is given by

    [itex]\hat{H}_0 = \frac{\hbar \omega}{2}\left[\left|1\right\rangle\left\langle1\right| - \left|0\right\rangle\left\langle0\right|\right][/itex]

    find the eigenvalues and eigenstates

    2. Relevant equations

    3. The attempt at a solution

    so i formulated this operator as a matrix

    [itex]\frac{\hbar \omega}{2}
    \left( \begin{array}{cc}
    -1 & 0 \\
    0 & 1 \\ \end{array} \right)
    and found the eigenvalues to be -1 and 1

    but when i put them back into the eigenvalue equation Hx = λx [x is a 2 row column vector with elements x1 and x2]
    i get nonsense, something like

    for λ=1:
    x1 = -x1
    x2 = x2

    for λ=-1:
    x1 = x1
    x2 = -x2

    am i missing something important here?

  2. jcsd
  3. Jan 11, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Those look fine with no nonsense. Try solving each set of equations. One equation will fix one component, while the other doesn't fix anything. This is because, as with any eigenvector equation, a multiple of a solution is still a solution. You should just pick a convenient choice for the unknown variable in order to write down a solution.
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