\begin{tikzpicture}
\begin{umlstate}[name=state]{state}
\umlbasicstate[name=state1]{sub state1}
\umlbasicstate[x=4, name=state2]{sub state2}

\umlVHVtrans[arm1=-2cm]{state1}{state2}
\end{umlstate}
\end{tikzpicture}