added a label

thesis/chapters/quantum_computing.tex

@@ -84,6 +84,7 @@ A general $n$-qbit state can then be written as a superposition of the
 integer states:
 
 \begin{equation}
+    \label{eq:ci}
     \ket{\psi} = \sum\limits_{i = 0}^{2^n - 1} c_i \ket{i} 
 \end{equation}