سلام
بصورت زیر:
\documentclass[a4paper,12pt]{report}
\usepackage{tikz,amsmath,amssymb}
\tikzstyle{vertex}=[circle,draw,inner sep=0pt,minimum size=5pt]
\newcommand{\vertex}{\node[vertex]}
\begin{document}
\begin{center}
\begin{tikzpicture}[>=latex]
\vertex [fill](a1) at (0,0) [label=left:$0$]{};
\vertex [fill](b1) at (0,-3.5) [label=left:$1$]{};
\vertex [fill](a2) at (3.5,0) [label=right:$0$]{};
\vertex [fill](b2) at (3.5,-3.5) [label=right:$1$]{};
\path
(a1) edge[thick,->] node[below]{$1-\epsilon$}(a2)
(a1) edge[->] node[pos=0.8,anchor=south west]{$\epsilon$}(b2)
(b1) edge [->] node[pos=0.8,anchor=north west]{$\epsilon$}(a2)
(b1) edge[thick,->] node[above]{$1-\epsilon$} (b2);
\end{tikzpicture}
\end{center}
\end{document}
برای پیکان مثلثی، دستور >=latex
نوشتم.
خروجی: