Universal Quantum Cloning Machines for Two Identical Mixed Qubits
Yang Shuai, Meisheng Zhao, Nai-Le Liu, Zeng‐Bing Chen · Chinese Physics Letters · 2007
We present a series of universal quantum cloning machines for two identical mixed qubits. Every machine is optimal in the sense that it achieves the optimal bound of the single copy shrinking factor. Unlike in the case of pure state cloning, the single copy shrinking factor does not uniquely determine the cloning map in the case of mixed state cloning.