\begin{picture}(10,0)(0,0)
  \node(A)(20,0){}
  \node[Nframe=n](B)(0,0){}
\drawloop[loopangle=0](A){$\tau_1:g_1\to a_1$}
\drawloop[loopangle=90](A){$\tau_2:g_2\to a_2$}
\drawedge(B,A){$P_0$}
\end{picture}
