  The realization of robust coherent energy transfer with a long range from a
donor to an acceptor has many important applications in the field of quantum
optics. However, it is hard to be realized using conventional schemes. Here, we
demonstrate theoretically that the robust energy transfer can be achieved using
a photonic crystal platform, which includes the topologically protected edge
state and zero-dimensional topological corner cavities. When the donor and the
acceptor are put into a pair of separated topological cavities, respectively,
the energy transfer between them can be fulfilled with the assistance of the
topologically protected interface state. Such an energy transfer is robust
against various kinds of defects, and can also occur over very long distances,
which is very beneficial for biological detections, sensors, quantum
information science and so on.
