We analyze various eavesdropping strategies on a quantum cryptographic channel. We present the optimal strategy for an eavesdropper restricted to a two-dimensional probe, interacting on-line with each transmitted signal. The link between safety of the transmission and the violation of Bell's inequality is discussed. We also use a quantum copying machine for eavesdropping and for broadcasting quantum information.
@article{arxiv.quant-ph/9611041,
title = {Quantum Cloning, Eavesdropping and Bell's inequality},
author = {N. Gisin and B. Huttner},
journal= {arXiv preprint arXiv:quant-ph/9611041},
year = {2009}
}