# Quantum copying: Beyond the no-cloning theorem.

@article{Buzek1996QuantumCB, title={Quantum copying: Beyond the no-cloning theorem.}, author={Buzek and Hillery}, journal={Physical review. A, Atomic, molecular, and optical physics}, year={1996}, volume={54 3}, pages={ 1844-1852 } }

We analyze the possibility of copying ~that is, cloning! arbitrary states of a quantum-mechanical spin-1/2 system. We show that there exists a ‘‘universal quantum-copying machine’’ ~i.e., transformation! which approximately copies quantum-mechanical states such that the quality of its output does not depend on the input. We also examine a machine which combines a unitary transformation and a selective measurement to produce good copies of states in the neighborhood of a particular state. We…

## 64 Citations

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