Quantum-key-expansion protocol based on number-state-entanglement-preserving tensor network with compression

Abstract

Quantum-key-distribution (QKD) protocols allow exchanging a cryptographic key between two parties. With the development of the Internet, however, all forms of communications consume a huge number of cryptographic keys. Improving the secure key rate of QKD is becoming increasingly important. Quantum compression and key expansion are two ways to increase the secure key rate. In this paper, we propose a quantum-key-expansion (QKE) protocol. A series of singlet states are compressed by number-state-entanglement-preserving tensors and disentanglers to obtain a compressed two-body-entangled state. The cryptographic key is expanded by the number-state-entanglement-preserving tensor network. The advantages of the proposed QKE protocol over the classical-key-expansion algorithm in the key-expansion method, the key length, and the security are discussed in this study. Moreover, due to the structure of the number-state-preserving compression tensor network, our protocol can resist the intercept-resend attack, entanglement-and-measurement attack, and coherent attack.