Phys. Rev. A 62, 012302 (2000) [7 pages]Phase-covariant quantum cloningReceived 14 September 1999; published 7 June 2000 We consider an N⃗M quantum cloning transformation acting on pure two-level states lying on the equator of the Bloch sphere. An upper bound for its fidelity is presented, by establishing a connection between optimal phase-covariant cloning and phase estimation. We give the explicit form of a cloning transformation that achieves the bound for the case N=1, M=2, and find a link between this case and optimal eavesdropping in the quantum cryptographic scheme BB84. © 2000 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevA.62.012302
DOI:
10.1103/PhysRevA.62.012302
PACS:
03.67.Dd, 03.65.-w
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