Unconditional Quantum Cloning of Coherent States with Linear Optics
Ulrik L. Andersen, Vincent Josse, Gerd Leuchs · Physical Review Letters · 2005
A scheme for optimal Gaussian cloning of optical coherent states is proposed and experimentally demonstrated. Its optical realization is based entirely on simple linear optical elements and homodyne detection. The optimality of the presented scheme is limited only by detection inefficiencies. Experimentally, we achieved a cloning fidelity of about 65%, which almost touches the optimal value of $2/3$.