\documentclass{standalone}
\usepackage{binarytree}

\begin{document}
\btreeset{%
  math labels,%
  separate,%
  level distance scales=false,%
  sibling distance scales=false,%
  continue after turn=false,%
  continue at path end=false,%
  left label anchor=center,%
  right label anchor=center}

\BinaryTree{l:\nwarrow!r:\nearrow,r:\nearrow!l:\nwarrow}{3}
\end{document}