A class of protocols for quantum private comparison based on the symmetry of states

In this paper, a class of protocols for quantum private comparison is investigated. The main feature is that the symmetry of quantum states is utilized. First of all, we design a new protocol for quantum private comparison via the χ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\chi $$\end{document}-type state as a special example. Then, through the in-deep research and analysis on the quantum carrier, it is found that lots of quantum states with the symmetrical characteristic can be utilized to perform the protocol successfully. It is an attractive advantage in the practical application. What is more, two players are only required to be equipped with the unitary operation machines. It means that our protocols can easily be realized and have a broad scope of application. Finally, the analyses on the protocols’ security, which are mainly ensured by the symmetry of quantum states and the property of the decoy state, are given in detail.