\documentclass[crop,tikz,convert=pdf2svg]{standalone}
\usepackage{color}

% Tikz settings optimized for causal graphs.
\usetikzlibrary{shapes,decorations,arrows,calc,arrows.meta,fit,positioning}
\tikzset{
    -Latex,auto,node distance =1 cm and 1 cm, semithick ,
    state/.style ={ellipse, draw, minimum width = 0.7 cm},
    point/.style = {circle, draw, inner sep=0.04cm,fill,node contents={}},
    bidirected/.style={Latex-Latex,dashed},
    el/.style = {inner sep=2pt, align=left, sloped}
}

\begin{document}

% The graph
\begin{tikzpicture}

    % X and Y nodes
    \node[state] (x) at (0,0) {$X$};
    \node[state] (y) [right = of x] {$Y$};

    % Directed edge
    \path (x) edge (y);

    % Bidirected edge
    \path[bidirected] (x) edge[bend left=60] (y);

\end{tikzpicture}

\end{document}