Step 1: Eigenvalues of the matrix.
To find the eigenvalues of the matrix, we compute its characteristic equation:
\[
\text{det} \left( A - \lambda I \right) = 0.
\]
This gives us the characteristic polynomial, from which we can solve for the eigenvalues \( \alpha, \beta, \gamma, \delta \). The determinant leads to the eigenvalues \( 0, 1, 2, 3 \).
Step 2: Computing the sum of squares.
We compute \( \alpha^2 + \beta^2 + \gamma^2 + \delta^2 \), which gives:
\[
0^2 + 1^2 + 2^2 + 3^2 = 0 + 1 + 4 + 9 = 6.
\]