A 4-port network has the scattering matrix as shown

\(\left[ S \right]=\left[ \begin{matrix} 0.1\angle 90{}^\circ & 0.8\angle -45 & 0.3\angle -45 & a \\ 0.8\angle -45{}^\circ & 0 & 0 & 0.4\angle 45{}^\circ \\ 0.3\angle -45{}^\circ & 0 & 0 & 0.6\angle -45{}^\circ \\ a & 0.4\angle 45{}^\circ & 0.4\angle -45{}^\circ & 0 \\ \end{matrix} \right]\) 

For the network to be lossless the value of |a| is _________.