Long-distance distribution of genuine energy-time entanglement

Year: 2013

Authors: Cuevas A., Carvacho G., Saavedra G., Carise J., Nogueira W.A.T., Figueroa M., Cabello A., Mataloni P., Lima G., Xavier G.B.

Autors Affiliation: Departamento de Fısica, Universidad de Concepcion, 160-C, Concepcion 4070386, Chile; Center for Optics and Photonics, Universidad de Concepcion, Concepcion 4070386, Chile; MSI-Nucleus for Advanced Optics, Universidad de Concepcion, Concepcion 4070386, Chile; Departamento de Ingenierıa Electrica, Universidad de Concepcion, 160-C, Concepcion 4070386, Chile; Departamento de Fısica Aplicada II, Universidad de Sevilla E-41012, Sevilla, Spain; Dipartimento di Fisica, Sapienza Universita` di Roma, Piazzale Aldo Moro 5, Roma I-00185, Italy; Istituto Nazionale di Ottica (INO-CNR), Largo E. Fermi 6 I-50125, Firenze, Italy

Abstract: Any practical realization of entanglement- based quantum communication must be intrinsically secure and able to span long distances avoiding the need of a straight line between the communicating parties. The violation of Bell’s inequality offers a method for the certification of quantum links without knowing the inner workings of the devices. Energy-time entanglement quantum communication satisfies all these requirements. However, currently there is a fundamental obstacle with the standard configuration adopted: an intrinsic geometrical loophole that can be exploited to break the security of the communication, in addition to other loopholes. Here we show the first experimental Bell violation with energy-time entanglement distributed over 1 km of optical fibres that is free of this geometrical loophole. This is achieved by adopting a new experimental design, and by using an actively stabilized fibre-based long interferometer. Our results represent an important step towards long-distance secure quantum communication in optical fibres.

Journal/Review: NATURE COMMUNICATIONS

Volume: 4      Pages from: 2871-1  to: 2871-6

More Information: The authors thank M. Barbieri for valuable discussions. This work was supported by the grants FONDECYT 11110115 and 1120067, CONICYT PFB08-024 and Milenio P10-030-F. A. Cuevas, G.C. and J.C. acknowledge the financial support of CONICYT, while M.F. acknowledges support of FONDECYT 1121010. A. Cabello was also supported by Project No. FIS2011-29400 (MINECO, Spain).
KeyWords: Quantum Cryptography; Bell-inequality; Local Realism; Violation; Photons; Fiber
DOI: 10.1038/ncomms3871

Citations: 40
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