Abstract
Subtle quantum properties offer exciting new prospects in optical communications. For example, quantum entanglement enables the secure exchange of cryptographic keys1 and the distribution of quantum information by teleportation2,3. Entangled bright beams of light are increasingly appealing for such tasks, because they enable the use of well-established classical communications techniques4. However, quantum resources are fragile and are subject to decoherence by interaction with the environment. The unavoidable losses in the communication channel can lead to a complete destruction of entanglement5,6,7,8, limiting the application of these states to quantum-communication protocols. We investigate the conditions under which this phenomenon takes place for the simplest case of two light beams, and analyse characteristics of states which are robust against losses. Our study sheds new light on the intriguing properties of quantum entanglement and how they may be harnessed for future applications.
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Acknowledgements
This work was funded by the Brazilian agencies Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). It was performed as part of the Brazilian National Institute of Science and Technology for Quantum Information. K.N.C. and A.S.V. acknowledge support from the Alexander von Humboldt Foundation. We thank D. Elser for assistance in an earlier stage of the experiment.
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F.A.S.B. and A.S.C. performed the experiments and participated in data analysis, discussions and writing the manuscript. A.J.F., K.N.C. and A.S.V. participated in data analysis, discussions and writing the manuscript. P.N. and M.M. were responsible for general planning and participated in data analysis, discussions and writing the manuscript.
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Barbosa, F., Coelho, A., de Faria, A. et al. Robustness of bipartite Gaussian entangled beams propagating in lossy channels. Nature Photon 4, 858–861 (2010). https://doi.org/10.1038/nphoton.2010.222
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DOI: https://doi.org/10.1038/nphoton.2010.222
