Multipartite quantum cryptography based on the violation of Svetlichny’s inequality

Abstract

Multipartite cryptography is useful for some particular missions. In this paper, we present a quantum key distribution scheme in which three separated observers can securely share a set of keys by using a sequence of 3-particle GHZ states. We prove that the violation of Svetlichny’s inequality can be utilized to test for eavesdropping, and even when the eavesdropper can completely control the outcomes of two participants’ measurements, our scheme still ensures the security of the keys distribution. This scheme can be easily extended to the case of N-party keys distribution, and the violation of N-partite Svetlichny’s inequality guarantees the security of the generalized scheme. Since the GHZ state has maximum entanglement, its perfect monogamy guarantee the device-independent security of our protocol. However, quantum entanglement is a vulnerable resource which is often decayed during transmission, so we need here to derive the secret-key rate of our protocol under the condition of using quantum states with non-maximal entanglement. We then calculate the extractable secret-key rate of the three-party key distribution protocol for the Werner state in the device-independent scenario. We find that the value of the extractable secret-key rate monotonously approaches 1 as the value of the visibility of the Werner state increases, and it reaches its maximum value 1 when the Werner state becomes the GHZ state.