Minor edits

Advanced/Introduction to Quantum/src/parts/04 logic gates.tex

@@ -76,6 +76,7 @@ The \texttt{and} gate is a map $\mathbb{B}^2 \to \mathbb{B}$ defined by the foll
 \end{center}
 
 Find a matrix $A$ so that $A\ket{\texttt{ab}}$ works as expected. \par
+\hint{Remember, we write bits as vectors.}
 
 
 \begin{solution}