Abstract
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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Acknowledgements
We acknowledge support by the Swedish Research Council (Vetenskapsrådet).
Author information
Affiliations
Physics Department, Stockholm University, S-10691, Stockholm, Sweden
- Elias Amselem
- & Mohamed Bourennane
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Contributions
E.A. carried out the experiment. E.A. and M.B. discussed the results and wrote the manuscript. M.B. supervised the project.
Corresponding author
Correspondence to Mohamed Bourennane.
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