cant understand the way the book tests if a matrix is totaly positive(dont know the proper term)

we need to show that $\displaystyle \sum_{i=1}^{2}\sum_{j=1}^{2}a_{ij}k_{i}\overline{k _{j}}>0$

ihave this matrix but

$\displaystyle \left(\begin{array}{cc}0 & i\\-i & 0\end{array}\right)$

so they choose $\displaystyle k_{1}=1$$\displaystyle k_{2}=0$ and got that the expession is =0

but we have 4 members here

so we need k for each member thus we need 4 k's

why 2?

cant understand how this method works

?