Abstract
We consider an 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 and find a link between this case and optimal eavesdropping in the quantum cryptographic scheme BB84.
- Received 14 September 1999
DOI:https://doi.org/10.1103/PhysRevA.62.012302
©2000 American Physical Society