Semi-quantum Secure Direct Communication Scheme Based on Bell States

Recently, the idea of semi-quantumness has been often used in designing quantum cryptographic schemes, which allows some of the participants of a quantum cryptographic scheme to remain classical. One of the reasons why this idea is popular is that it allows a quantum information processing task to be accomplished by using quantum resources as few as possible. In this paper, we extend the idea to quantum secure direct communication(QSDC) by proposing a semi-quantum secure direct communication scheme. In the scheme, the message sender, Alice, encodes each bit into a Bell state |φ+〉=12(|00〉+|11〉)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$|\varphi ^{+}\rangle =\frac {1}{\sqrt 2}(|00\rangle +|11\rangle )$\end{document} or |Ψ+〉=12(|01〉+|10〉)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$|{\Psi }^{+}\rangle =\frac {1}{\sqrt 2}(|01\rangle +|10\rangle )$\end{document}, and the message receiver, Bob, who is classical in the sense that he can either let the qubit he received reflect undisturbed, or measure the qubit in the computational basis |0〉, |1〉 and then resend it in the state he found. Moreover, the security analysis of our scheme is also given.