摘要
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 reta/ned and the CQSDC can be really realized.
基金
The project supported by the Program of New Century Excellent Talents at the University of China under Grant No.NCET-06-0554
National Natural Science Foundation of China under Grant Nos.60677001 and 10747146
the Science-Technology Fund of Anhui Province for Outstanding Youth under Grant No.06042087
the Key Fund of the Ministry of Education of China under Grant No.206063
the Natural Science Foundation of Guangdong Province under Grant Nos.06300345 and 7007806
the Natural Science Foundation of Hubei Province under Grant No.2006ABA354
