Multipartite Einstein-Podolsky-Rosen (EPR) steering is a useful quantum resource for quantum communication in quantum networks. It has potential applications in secure quantum communication, such as one-sided deviceindependent quantum key distribution and quantum secret sharing. By distributing optical modes of a multipartite entangled state to space-separated quantum nodes, a local quantum network can be established. Based on the existing multipartite EPR steering in a local quantum network, secure quantum communication protocol can be accomplished. In this manuscript, we present swapping schemes for EPR steering between two space-separated Gaussian multipartite entangled states, which can be used to connect two space-separated quantum networks. Two swapping schemes, including the swapping between a tripartite Greenberger-Horne-Zeilinger (GHZ) entangled state and an EPR entangled state and that between two tripartite GHZ entangled states, are analyzed. Various types of EPR steering are presented after the swapping of two space-separated independent multipartite entanglement states without direct interaction, which can be used to implement quantum communication between two quantum networks. The presented schemes provide technical reference for more complicated quantum networks with EPR steering.

Motivated by the quantum Fourier transform (QFT), a sequential quantum multiparty signature (QMS) scheme is proposed. Several signatories jointly accomplish the task in a chaotic encryption system. Alice generates and sends the encrypted message with the quantum Fourier transform. Signatories provide individual signatures in a certain order, while Bob verifies the authenticity of the combined multiple signatures after the eavesdropping check phase with help of the arbitrator. Analysis shows the correctness and security of the proposed scheme. This QMS protocol increases the efficiency of verification compared to arbitrated quantum signatures and broadcasting multiparty signature. This QMS protocol will be widely used for online e-government and e-business systems.

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