Quantum properties in the four-node network

There are different preparable quantum states in different network structures. The four nodes as a whole has two situations: one is the four nodes in a plane, the other is the four nodes in the space. In this paper, we obtain some properties of the quantum states that can be prepared in four-node network structures. These include the properties of entropy, entanglement measure, rank and multipartite entangled states. These properties also mean that the network structures impose some constraints on the states that can be prepared in a four-node quantum network. In order to obtain these properties we also define $n$-partite mutual information of the quantum system, which satisfies symmetry requirement.