Entanglement of Formation of 1��2 Quantum cloners

Eui-Soon Yim

임의순

Manish Kumar Shukla, Indranil Chakrabarty, Sourav Chatterjee

Evgueni Karpov, Patrick Navez, Nicolas J. Cerf

We derive a quantum cloning machine that maximizes the entanglement of formation of the two copies of any maximally entangled input state, while preserving the separability of all unentangled input states. In addition, it is proven to optimally duplicate the entanglement of formation of all isotropic input states. For large d , the cloning machine behaves classically and outperforms a local entanglement cloner, studied for comparison.

Dagmar Bruß, Chiara Macchiavello

Evgueni Karpov, Patrick Navez, Nicolas J. Cerf

We have found a quantum cloning machine that optimally duplicates the entanglement of a pair of $d$-dimensional quantum systems prepared in an arbitrary isotropic state. It maximizes the entanglement of formation contained in the two copies of any maximally entangled input state, while preserving the separability of unentangled input states. Moreover, it cannot increase the entanglement of formation of isotropic states. For large $d$, the entanglement of formation of each clone tends to one-half the entanglement of the input state, which corresponds to a classical behavior. Finally, we investigate a local entanglement cloner, which yields entangled clones with one-fourth the input entanglement in the large-$d$ limit.