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Quantum teleportation across a metropolitan fibre network


If a photon interacts with a member of an entangled photon pair via a Bell-state measurement (BSM), its state is teleported over principally arbitrary distances onto the pair's second member1. Since 1997, this puzzling prediction of quantum mechanics has been demonstrated many times2. However, with two exceptions3,4, only the photon that received the teleported state, if any, travelled far, while the photons partaking in the BSM were always measured close to where they were created. Here, using the Calgary fibre network, we report quantum teleportation from a telecom photon at 1,532 nm wavelength, interacting with another telecom photon after both have travelled several kilometres and over a combined beeline distance of 8.2 km, onto a photon at 795 nm wavelength. This improves the distance over which teleportation takes place to 6.2 km. Our demonstration establishes an important requirement for quantum repeater-based communications5 and constitutes a milestone towards a global quantum internet6.

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Figure 1: Aerial view of Calgary.
Figure 2: Schematics of the experimental set-up.
Figure 3: Indistinguishability of photons at Charlie.
Figure 4: Density matrices of four states after teleportation.
Figure 5: Individual and average fidelities of four teleported states with expected (ideal) states, measured using quantum state tomography (QST) and the decoy-state method (DSM).


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The authors thank T. Andruschak, R. Angelo, D. Basto, C. Chambers and H. Dhillon from the City of Calgary for providing access to the fibre network and for help during the experiment, V. Kiselyov for technical support and P. Lefebvre for help with aligning the entangled photon pair source. This work was funded through Alberta Innovates Technology Futures (AITF), the National Science and Engineering Research Council of Canada (NSERC) and the Defense Advanced Research Projects Agency (DARPA) Quiness programme (contract no. W31P4Q-13-l-0004). W.T. also acknowledges funding as a Senior Fellow of the Canadian Institute for Advanced Research (CIFAR), and V.B.V. and S.W.N. acknowledge partial funding for detector development from the Defense Advanced Research Projects Agency (DARPA) Information in a Photon (InPho) programme. Part of the detector research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

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The SNSPDs were fabricated and tested by V.B.V., F.M., M.D.S. and S.W.N. The experiment was conceived and guided by W.T. The set-up was developed, measurements were performed, and the data were analysed by R.V., M.G.P., Q.Z., G.H.A. and D.O. The manuscript was written by W.T., R.V., M.G.P., Q.Z., G.H.A. and D.O.

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Correspondence to Wolfgang Tittel.

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The authors declare no competing financial interests.

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Valivarthi, R., Puigibert, M., Zhou, Q. et al. Quantum teleportation across a metropolitan fibre network. Nature Photon 10, 676–680 (2016).

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