DOC.md

Order bra-ket identical to order row-col

Consider density matrix $\rho = \ket{a}\bra{b}$, we can construct this by a[1] ^ b[1]. Contracting this will give $\rho$. Let’s consider the following case:

$$ A = \begin{bmatrix} 1 \ 2 \end{bmatrix}

\begin{bmatrix} 3 & 4 \end{bmatrix} =

\begin{bmatrix} 3 & 4 \ 6 & 8 \end{bmatrix} $$

Setting the row’s index to 1 is equivalent to picking the first element in $\ket{a}$. We can generalize this to any number of qubits and we can say the orders are equivalent.