\begin{array}{cccc}
\begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{1, 1}~\mbox{on}~U_{1, 1}} & \qw
} \end{array} & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{2, 1}~\mbox{on}~U_{2, 1}} & \qw
} \end{array} & \cdots & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{n, 1}~\mbox{on}~U_{n, 1}} & \qw
} \end{array} \\
\begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{1, 2}~\mbox{on}~U_{1, 2}} & \qw
} \end{array} & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{2, 2}~\mbox{on}~U_{2, 2}} & \qw
} \end{array} & \cdots & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{n, 2}~\mbox{on}~U_{n, 2}} & \qw
} \end{array} \\
\vdots & \vdots & \ddots & \vdots \\
\begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{1, k}~\mbox{on}~U_{1, k}} & \qw
} \end{array} & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{2, k}~\mbox{on}~U_{2, k}} & \qw
} \end{array} & \cdots & \begin{array}{c} \Qcircuit@C=1em @R=.7em{
& & \gate{D_{n, k}~\mbox{on}~U_{n, k}} & \qw
} \end{array} \\
\end{array}