量子克隆被认为对量子密码术最优的个体窃听.特别的,最优相位协变量子克隆被认为是BB84方案的最优个体攻击.本文我们利用Cerf’s形式,严格的证明两维空间中1—2非对称经济型相位协变量子克隆的最优性.证明中,我们得出另一种独立的幺正变换.我们的结果涵盖了以前的结果[Durt T,et al.Phys.Rev.A,2004,69:062316].
Quantum cloning can be reviewed as the optimal individual eavesdropping on quantum cryptography. Specifically, the optimal phase-covariant cloning is regarded as the optimal individual attack on the BB84 protocol. In this paper, by exploring Cerf's formalism, we prove the optimality of the asymmetric economical 1→2 phase-covariant quantum cloning in 2 dimensions working without ancilla. In proof, we derive another independent unitary transformation of this cloner. Our result covers previous contributions [ Durt T, et al. Phys. Rev. A, 2004, 69: 062316].