Optimal Cloning of Coherent States with a Linear Amplifier and Beam Splitters
Samuel L. Braunstein, Nicolas J. Cerf, S. Iblisdir, Peter van Loock, Serge Massar · Physical Review Letters · 2001
A transformation achieving the optimal symmetric N-->M cloning of coherent states is presented. Its implementation requires only a phase-insensitive linear amplifier and a network of beam splitters. An experimental demonstration of this continuous-variable cloner should therefore be in the scope of current technology. The link between optimal quantum cloning and optimal amplification of quantum states is also pointed out.