In Eq. (7) the variable \( n \) represents the number of time steps. If we define \( n=t/\Delta t \), we can then couple the variance result from a random walk in one dimension with the variance from the diffusion equation of Eq. (6) by defining the diffusion constant as $$ \begin{equation*} D = \frac{l^2}{\Delta t}. \end{equation*} $$