\documentclass[tikz]{standalone}

\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{braket}

\usepackage{tikz}
\usetikzlibrary{arrows, arrows.meta, calc, decorations, positioning}

% load TikZ grafic definitions
%\input{gfx_TikZ}

% main document
\begin{document}

	\begin{tikzpicture}[]

	\def\tensorSize{0.2}

		\begin{scope}

			% label
			\node at (+3.5,0) {\large$\rho_\text{DR}^{[x+1,y+1]}$};

			% network corrdinates
			\coordinate (PN) at (+0.0, +0.5);
			\coordinate (PC) at (+0.0, -0.5);
			\coordinate (T2) at (+2.0, -0.0);
			\coordinate (C3) at (+0.5, -1.5);
			\coordinate (T3) at (-1.5, -1.5);
			
			% external links
			\draw[ultra thick] ($(T2) + (+1.25, +1.25)$) to (T2) node at ($(T2) + (+1.50, +1.50)$) {$-1$};
			\draw[thick] ($(PC) + (+1.75, +1.75)$) to (PC) node at ($(PC) + (+2.00, +2.00)$) {$-2$};
			\draw[thick] ($(PN) + (+0.75, +0.75)$) to (PN) node at ($(PN) + (+1.00, +1.00)$) {$-3$};
			\draw[ultra thick] ($(T3) + (-1.50, +0.00)$) to (T3) node at ($(T3) + (-2.00, +0.00)$) {$-4$};
			\draw[thick] (PC) to ($(PC) + (-2.00, +0.00)$) node at ($(PC) + (-2.50, +0.00)$) {$-5$};
			\draw[thick] (PN) to ($(PN) + (-1.00, +0.00)$) node at ($(PN) + (-1.50, +0.00)$) {$-6$};

			% internal links
			\draw[ultra thick] (T2) to (C3) node[right = 0.25] at ($(T2)!0.5!(C3)$) {$2$};
			\draw[thick] (T2) to [out = 180, in =   0] (PC) node[below] at ($(T2)!0.7!(PC)$) {$6$};
			\draw[ultra thick] (C3) -- (T3) node [midway, below] {$1$};
			\draw[thick] (PC) to [out = 225, in = 45] (T3) node[below right] at ($(PC)!0.3!(T3)$) {$5$};
			\draw[thick] (T2) to [out = 180, in =   0] (PN) node[above] at ($(T2)!0.3!(PN)$) {$4$};
			\draw[thick] (PN) to [out = 225, in = 45] (T3) node[left] at ($(PN)!0.7!(T3)$) {$3$};
			\draw[thick] (PN) -- (PC) node [midway, right] {$7$};

			% CTMRG tensors
			\foreach \tensor in {T2, C3, T3} {
				\draw[thick,black,fill = gray] (\tensor) circle (\tensorSize);
			}

			% iPEPS tensors
			\foreach \tensor in {PN, PC} {
				\draw[thick,black,fill = blue] (\tensor) circle (\tensorSize);
			}
			
		\end{scope}

	\end{tikzpicture}

\end{document}

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