\documentclass[11pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{physics}
\usepackage{yquant}


\begin{document}

\section{Spacer}

\yquantdefinebox{dots}[inner sep=0pt]{$\vdots$}
\begin{tikzpicture}
	\begin{yquant}[register/separation=0mm]
		qubit {$\ket{x_1}$} x1;
		qubit {$\ket{x_2}$} x2;
		qubit {$\ket{x_3}$} x3;
		nobit xdots;
		qubit {$\ket{x_{n\!-\!1}}$} xn1;
		qubit {$\ket{x_n}$} xn;

		h x1;
		box {$R_2$} x1 | x2;
		box {$R_3$} x1 | x3;
		align x1, x2, x3, xdots, xn1, xn;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x2;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x3;
		[draw=none]
		box {$\ddots$} xdots;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn;
		[operator/separation=0mm]
		box {$R_{n\!-\!1}$} x1 | xn1;
		box {$R_n$} x1 | xn;

		h x2;
		box {$R_2$} x2 | x3;
		align x1, x2, x3, xdots, xn1, xn;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x2;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x3;
		[draw=none]
		box {$\ddots$} xdots;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn;
		[operator/separation=0mm]
		box {$R_{n\!-\!2}$} x2 | xn1;
		box {$R_{n\!-\!1}$} x2 | xn;

		align x1, x2, x3, xdots, xn1, xn;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x1;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x2;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x3;
		[draw=none, operator/separation=3mm]
		box {$\ddots$} xdots;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} xn1;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} xn;

		align x1, x2, x3, xdots, xn1, xn;
		[operator/separation=3mm]
		h xn1;
		box {$R_2$} xn1 | xn;

		h xn;

		[value=$\ket{k_n}$]
		output x1;
		[value=$\ket{k_{n\!-\!1}}$]
		output x2;
		[value=$\ket{k_{n\!-\!2}}$]
		output x3;
		[value=$\ket{k_2}$]
		output xn1;
		[value=$\ket{k_1}$]
		output xn;
	\end{yquant}
\end{tikzpicture}

\section{Spacer}


\begin{tikzpicture}
	\begin{yquant}[register/separation=0mm]
		qubit {$\ket{x_1}$} x1;
		qubit {$\ket{x_2}$} x2;
		qubit {$\ket{x_3}$} x3;
		nobit xdots;
		qubit {$\ket{x_{n\!-\!1}}$} xn1;
		qubit {$\ket{x_n}$} xn;

		h x1;
		box {$R_2$} x1 | x2;
		box {$R_3$} x1 | x3;
		align x1, x2, x3, xdots, xn1, xn;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x2;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} x3;
		[draw=none]
		box {$\ddots$} xdots;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn1;
		[draw=none]
		box {$\!\cdot\!\cdot\!\cdot\!$} xn;
		[operator/separation=0mm]
		box {$R_{n\!-\!1}$} x1 | xn1;
		box {$R_n$} x1 | xn;

		align x1, x2, x3, xdots, xn1, xn;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x1;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x2;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} x3;
		[draw=none, operator/separation=3mm]
		box {$\ddots$} xdots;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} xn1;
		[draw=none, operator/separation=3mm]
		box {$\cdots$} xn;

		align x1, x2, x3, xdots, xn1, xn;
		[operator/separation=3mm]
		h xn1;
		box {$R_2$} xn1 | xn;

		h xn;

		swap (x1, xn);
		swap (x2, xn1);
		swap (x3, xdots);

		[value=$\ket{k_1}$]
		output x1;
		[value=$\ket{k_{2}}$]
		output x2;
		[value=$\ket{k_{3}}$]
		output x3;
		[value=$\ket{k_{n-1}}$]
		output xn1;
		[value=$\ket{k_n}$]
		output xn;
	\end{yquant}
\end{tikzpicture}

\end{document}