  Inside a three-dimensional strong topological insulator, a tube with $h/2e$
magnetic flux carries a pair of protected one-dimensional linear fermionic
modes. This phenomenon is known as the "wormhole effect". In this work, we find
that the "wormhole effect", as a unique degree of freedom, introduces exotic
transport phenomena and thus manipulates the transport properties of
topological insulators. Our numerical results demonstrate that the transport
properties of a double-wormhole system can be manipulated by the wormhole
interference. Specifically, the conductance and local density of states both
oscillate with the Fermi energy due to the interference between the wormholes.
Furthermore, by studying the multi-wormhole systems, we find that the number of
wormholes can also modulate the differential conductance through a
$\mathbb{Z}$$_{2}$ mechanism. Finally, we propose two types of topological
devices in real applications, the "wormhole switch" device and the "traversable
wormhole" device, which can be finely tuned by controlling the wormhole degree
of freedom.
