Comment on “Optimal encryption of quantum bits”
Xiangfu Zou, Daowen Qiu · Physical Review A · 2013
Boykin and Roychowdhury [Phys. Rev. A 67, 042317 (2003)] discussed the optimal encryption of quantum bits, gave a necessary and sufficient condition (NASC) for the security of quantum encryption, and suggested an optimal quantum one-time pad encryption scheme. In this Comment, we point out that the proof of the NASC for the security of quantum encryption is not correct. Moreover, we reprove the NASC for the security of quantum encryption.