**5.2 Multi-hop QT networking mechanism**

In a QTN based on teleportation, the necessary conditions for the transmission of information-carrying quantum states between two nodes are: a quantum channel composed of entangled particle pairs must exist between the source node and the destination node. However, it is impossible for any two nodes in the network to share entangled particle pairs, which means that the source node may not be able to directly transmit information to any other node in the network. In order to achieve communication between remote nodes, intermediate nodes are introduced to assist in the transmission of information [18]. Therefore, when the sender and the receiver directly share the entangled particle pair, the two nodes can directly transmit the quantum state; otherwise, there needs to be at least a quantum path established between the sender and the receiver—a quantum path established through an intermediate node. Entangled particle pairs are shared between neighboring nodes. The method of using teleportation technology to achieve quantum information transmission through intermediate nodes is called multi-hop QT [37].

In the traditional multi-hop QT system, the hop-by-hop QT scheme is often used. In the hop-by-hop QT transmission process, it is necessary to measure the entanglement of the nodes on the path one by one. According to the measurement result of the previous node, perform a unitary transformation on the particles held by the node to restore to the quantum state to be transmitted. The transmission of quantum information is from the source node to the destination node. An efficient multi-hop QT scheme is proposed [37]. The measurement results of the source node and the intermediate node are uniformly transmitted to the destination node, and only the unitary transformation is performed at the destination node.
