Article abstract


Nature Physics 5, 748 - 752 (2009)
Published online: 23 August 2009 | doi:10.1038/nphys1372

Subject Categories: Quantum physics | Optical physics

Experimental four-qubit bound entanglement

Elias Amselem1 & Mohamed Bourennane1


Entanglement is one of the most puzzling features of quantum theory and of great importance for the new field of quantum information. Being a peculiar form of entanglement, bound entanglement emerges in certain mixed quantum states. This form of entanglement is not distillable by local operators and classical communication. Bound-entangled states are different from both the free entangled (distillable) and separable states. Here we report on the first experimental demonstration of a four-qubit polarization bound-entangled state, the so-called Smolin state. We have fully characterized its entanglement properties. Moreover, we have realized unlocking of the entanglement protocol for this state. The special properties of the Smolin state constitute a useful quantum resource for new multiparty communication schemes.

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  1. Physics Department, Stockholm University, S-10691, Stockholm, Sweden

Correspondence to: Mohamed Bourennane1 e-mail: boure@fysik.su.se



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