\documentclass[11pt]{article}
\input{Qcircuit}
\thispagestyle{empty}
\begin{document}
\begin{align*}
 \Qcircuit @C=1em @R=.7em {
  \lstick{\ket{x_3}} & \qw      & \qw              & \qw      & \ctrl{2}         & \ctrl{1}         & \gate{H} & \rstick{\ket{y_1}} \qw \\
  \lstick{\ket{x_2}} & \qw      & \ctrl{1}         & \gate{H} & \qw              & \gate{R_{\pi/2}} & \qw      & \rstick{\ket{y_2}} \qw \\
  \lstick{\ket{x_1}} & \gate{H} & \gate{R_{\pi/2}} & \qw      & \gate{R_{\pi/4}} & \qw              & \qw      & \rstick{\ket{y_3}} \qw
 }
\end{align*}
\end{document}