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Passively stable distribution of polarisation entanglement over 192 km of deployed optical fibre

: Wengerowsky, S.; Joshi, S.K.; Steinlechner, F.; Zichi, J.R.; Liu, B.; Scheidl, T.; Dobrovolskiy, S.M.; Molen, R. van der; Los, J.W.N.; Zwiller, V.; Versteegh, M.A.M.; Mura, A.; Calonico, D.; Inguscio, M.; Zeilinger, A.; Xuereb, A.; Ursin, R.

Fulltext ()

npj Quantum information 6 (2020), Art. 5, 5 pp.
ISSN: 2056-6387
Journal Article, Electronic Publication
Fraunhofer IOF ()
cables; chromatic dispersion; optical fiber; photon; polarization

Quantum key distribution (QKD) based on entangled photon pairs holds the potential for repeater-based quantum networks connecting clients over long distance. We demonstrate long-distance entanglement distribution by means of polarisation-entangled photon pairs through two successive deployed 96 km-long telecommunications fibres in the same submarine cable. One photon of each pair was detected directly after the source, while the other travelled the fibre cable in both directions for a total distance of 192 km and attenuation of 48 dB. The observed two-photon Bell state exhibited a fidelity 85 ± 2% and was stable over several hours. We employed neither active stabilisation of the quantum state nor chromatic dispersion compensation for the fibre.