Several two-party protocols for quantum private comparison using entanglement and dense coding

Quantum private comparison (QPC) allows at least two participants who do not trust each other to compare whether their secret data are the same while maintaining data privacy, in which the security is based on the principles of quantum mechanics. In this paper, we propose several QPC protocols using Bell states, genuinely entangled five-qubit states, four-qubit cluster states and χ-type states. In each of the proposed protocols, we use dense coding technology to make the qubit efficiency of the protocol reach 100%, which is much higher than that of most existing protocols. The quantum states acting as information carriers are transmitted through a circular path, which can effectively reduce resource consumption. Decoy photon technology and one-time-pad encryption are used to ensure the security of the proposed protocols, making both external and internal attacks invalid.