Phase Estimation

\usepackage{quantikz}

\begin{quantikz}
  \lstick{$|0\rangle$} & \gate{H} & \ctrl{2} & \gate{H} & \meter{} \\
  \lstick{$|0\rangle$} & \gate{H} & \ctrl{1} & \qw & \meter{} \\
  \lstick{$|u\rangle$} & \qw & \gate{U} & \gate{U^2} & \qw
\end{quantikz}