Quantum private comparison protocol based on the entanglement swapping between $$\chi ^+$$ χ + state and W-Class state

Abstract

Quantum private comparison (QPC) protocol, including Alice, Bob and the third party Charlie, aims at comparing Alice and Bob’s secret inputs correctly without leaking them. Firstly, $$\chi ^+$$ state and W-Class state are used to conduct the entanglement swapping in this protocol. Either the basis $$\{|\phi ^\pm \rangle ,|\psi ^\pm \rangle \}$$ or the basis $$\{|\chi ^\pm \rangle ,|\omega ^\pm \rangle \}$$ is chosen by Alice and Bob based on the predetermined value to measure the particle pairs. And three bits of secret inputs can be compared in this protocol in every comparison time, while most of previous QPC protocols can only compare one or two bits. The qubit efficiency of this protocol is 60% more than others, which are 50% at most. Secondly, if the eavesdropper intends to obtain the secret inputs, it is important and primary to get the measurement results of particle pairs. In this protocol, even if the eavesdropper gets the accurate particle pairs, he cannot get the right measurement results without the right basis. Finally, this protocol is analyzed to be able to defend the secret inputs against various kinds of attack.