Quantum Cloning.dvi

Quantum cloning has been a topic of considerable interest for many years. It turns out to be quantum limit for copying an input state and is closely related to linear amplification when talking about optical cloning. It is commonly stated that it is impossible to clone. In actuallity it is possible to clone perfectly, one just needs to know the input state. As Wootters and Zurek showed it is impossible to clone any arbitrary unknown state with perfect fidelity. This became affectionately known as the “no cloning theorem”, although it is more correctly called the no “perfect cloning theorem”. In fact, it may be safe to say that quantum information was founded based on this theorem.