A general multi-step N->M probabilistic optimal universal cloning protocol is presented together with the experimental realization of the (1 -> 3) and (2 -> 3) machines. Since the present method exploits the bosonic nature of the photons, it can be applied to any particle obeying to the Bose statistics. On a technological perspective, the present protocol is expected to find applications as a novel, multi-qubit symmetrizator device to be used in modern quantum information networks.
@article{arxiv.quant-ph/0412040,
title = {Realization of a General Multi-step Quantum Cloning Machine},
author = {L. Masullo and M. Ricci and F. De Martini},
journal= {arXiv preprint arXiv:quant-ph/0412040},
year = {2007}
}