Controllable and tunable topological multiport beam splitter in an extended Su-Schrieffer-Heeger array

We demonstrate a controllable and tunable topological beam splitter with a multiport based on the one-dimensional extended Su-Schrieffer-Heeger model, which supports the topological interface by introducing the nearest-neighbor (NN) coupling defect at the central site. The quantum state initially prepared at the interface can be transmitted with high fidelity to multiple output ports with equal or unequal probability on both sides of the model by modulating the NN coupling between the sites in the time domain. We show that the output port can be added by increasing the number of sublattices $a$. Especially, by setting the on-site potential energy, we can easily control the direction of the quantum state transfer process and ensure that this state is only transmitted to the multiple output ports on the left or multiple output ports on the right, which realizes the function of topological switching. Benefiting from the topological protection of the edge states, the quantum states can be transmitted with high fidelity even if there is the NN coupling disorder. Our work realizes a robust and multifunctional topological beam splitter.