Two qubit copying machine for economical quantum eavesdropping
Two qubit copying machine for economical quantum eavesdropping
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DOI：
10.1103/physreva.60.2764
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发表时间：
1998-10
影响因子：
2.9
通讯作者：
C. Niu;R. Griffiths
中科院分区：
文献类型：
--
作者：
C. Niu;R. Griffiths
我们研究了当处于任意态的单个量子比特与处于给定固定状态的另一个量子比特相互作用时发生的映射，该映射导致了两个量子比特系统上的某种么正变换，这实际上是第一个量子比特的两个副本。使用两个二维Hilbert空间的张量积的任意二维子空间的特殊表示，推广了通常的Schmidt分解，讨论了所得到的副本的质量的一般问题。我们展示的量子电路可以复制这种类型的任何两个量子比特复制机的结果。还考虑了复印机的简单随机推广(使用“经典”随机信号)。这些复制机提供了先前提出的用于BB84和B92量子密码协议的最佳窃听方案的简单实施例。
We study the mapping which occurs when a single qubit in an arbitrary state interacts with another qubit in a given, fixed state resulting in some unitary transformation on the two qubit system which, in effect, makes two copies of the first qubit. The general problem of the quality of the resulting copies is discussed using a special representation, a generalization of the usual Schmidt decomposition, of an arbitrary two-dimensional subspace of a tensor product of two 2-dimensional Hilbert spaces. We exhibit quantum circuits which can reproduce the results of any two qubit copying machine of this type. A simple stochastic generalization (using a ``classical'' random signal) of the copying machine is also considered. These copying machines provide simple embodiments of previously proposed optimal eavesdropping schemes for the BB84 and B92 quantum cryptography protocols.