Communications in Theoretical Physics
Revisiting Controlled Quantum Secure Direct Communication Using a Non-symmetric Quantum Channel with Quantum Superdense Coding
Jun Liu, Yimin Liu, Yan Xia, Zhanjun Zhang
Abstract
Recently Xia and Song [Phys. Lett. A 364 (2007) 117] have proposed a controlled quantum secure direct communication (CQSDC) protocol. They claimed that in their protocol only with the help of the controller Charlie, the receiver Alice can successfully extract the secret message from the sender Bob. In this letter, first we will show that within their protocol the controller Charlie's role could have been excluded if it were not for their unreasonable design. We then revise the Xia–Song CQSDC protocol such that its original advantages are retained and the CQSDC can be really realized.