  A quantum interface for two-way entanglement transfer between orbital angular
momentum degree of freedom in free space and time-energy degree of freedom in
optical fibers, provides a novel way toward establishing entanglement between
remote heterogeneous quantum nodes. Here, we experimentally demonstrate this
kind of transfer interface by using two interferometric cyclic gates. By using
this quantum interface, we perform two-way entanglement transfer for the two
degrees of freedom. The results show that the quantum entangled state can be
switched back and forth between orbital angular momentum and time-energy
degrees of freedom, and the fidelity of the state before and after switching is
higher than 90%. Our work demonstrates the feasibility and high performance of
our proposed transfer interface, and paves a route toward building a
large-scale quantum communication network.
