Two Semi-Quantum Key Distribution Protocols with G-Like States

To address the problem of key distribution between/among quantum parties and classical parties, two semi-quantum key distribution (SQKD) protocols are proposed based on G-like states. The participants could infer their counterparts’ measurement results from their initial quantum states with the correlation properties of G-like states. With the assistance of a third-party service, the three-party SQKD protocol could be implemented in the absence of a quantum channel between two classical users. The measure-resend operation is performed twice so that the CTRL particles generally discarded in previous protocols could be reused. The two semi-quantum key distribution protocols are more efficient than some typical SQKD protocols. Besides, security analysis manifests that the proposed protocols with semi-quantum conception are secure against some general attacks.