Multi-party semi-quantum secure direct communication protocol with cluster states

A new semi-quantum secure direct communication (SQSDC) protocol based on four-particle cluster states is designed. Different from the existing SQSDC protocols, this semi-quantum secure direct communication protocol includes two classical senders and one quantum receiver. The designed SQSDC protocol promises higher qubit efficiency than the previous SQSDC protocols by adopting the property of the four-particle cluster state to implement encoding operations. Moreover, the security of the proposed protocol under some common eavesdropping attacks is validated. Furthermore, the presented SQSDC protocol can be transformed into an efficient multi-party semi-quantum dialogue (SQD) protocol.