The Influence Of Local Entanglement Swapping To Quantum Networks Robustness

We use entanglement percolation to establish long-distance entanglement between arbitrary nodes of quantum random networks. It can effectively solve the problem of the exponential decay of quantum entanglement state with the increase of distance. En-tanglement percolation is divided into two kinds according to the operating situation of the quantum communication network. One is classic entanglement percolation without operation and one is quantum entanglement percolation with operation. In this paper, the quantum entanglement percolation is refers to the network with local entanglement swapping operation.We use quantum random network model to explore the changes of entanglement percolation threshold and the changes of robustness.Firstly, we constructed a quantum random network model. Bonds between nodes in the network is a pair of partially two-qubit entangled states. These states turn into maximally entangled state by a certain probability. In this paper, we will use the bond percolation model to analysis this transformation. There is a local entanglement swapping operation for the networks. This operation changes the local connection of the network, which also lead to the entire network topology structure is changed. It finds that entan-glement percolation threshold relates to the average degree of the networks by theoretical analysis and numerical simulation. The entanglement percolation threshold is lower after the local entanglement swapping operation.When the average degree of the node degree is operated, entanglement percolation threshold is the lowest. This will help build a suc-cessful quantum communication networks.Secondly, we use the site percolation model to analyze the robustness of quantum communication networks. When the network nodes suffer random attack, although two kinds of entanglement percolation threshold will be significantly reduced, the change is relatively low after local entanglement swapping operations. This shows that the local entanglement swapping can improve the robustness of the network. It also finds that network robustness obviously stronger with the increase of attacks after the operation. This will contribute to the design of quantum communication networks against attack scenarios.Finally, this paper analyzes underlying causes of the local quantum entanglement swapping operations how to improve the robustness of the communication network. It finds that the number of nodes with big degree is significantly increased after operating by analyzing the degree distribution of network. The more nodes with big degree, the stronger of network robustness.