Optimal universal quantum cloning and state estimation

被引:268
作者
Bruss, D
Ekert, A
Macchiavello, C
机构
[1] ISI, I-10133 Turin, Italy
[2] Univ Oxford, Clarendon Lab, Oxford OX1 3PU, England
[3] Dipartimento Fis A Volta, I-27100 Pavia, Italy
[4] INFM, I-27100 Pavia, Italy
关键词
D O I
10.1103/PhysRevLett.81.2598
中图分类号
O4 [物理学];
学科分类号
0702 ;
摘要
We derive a tight upper bound for the fidelity of a universal N --> M qubit cloner, valid for any M greater than or equal to N, where the output of the cloner is required to be supported on the symmetric subspace. Our proof is based on the concatenation of two cloners and the connection between quantum cloning and quantum state estimation. We generalize the operation of a quantum cloner to mixed and/or entangled input qubits described by a density matrix supported on the symmetric subspace of the constituent qubits. We also extend the validity of optimal state estimation methods to inputs of this kind. [S0031-9007(98)07141-5].
引用
收藏
页码:2598 / 2601
页数:4
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