Semi-quantum Secure Direct Communication Scheme Based on Bell States

Abstract

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 $|\varphi ^{+}\rangle =\frac {1}{\sqrt 2}(|00\rangle +|11\rangle )$ or $|{\Psi }^{+}\rangle =\frac {1}{\sqrt 2}(|01\rangle +|10\rangle )$ , 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.