Letter abstract
Nature Physics 5, 389 - 392 (2009)
Published online: 3 May 2009 | doi:10.1038/nphys1255
Subject Categories: Quantum physics | Techniques and instrumentation | Information theory and computation
High-fidelity transmission of entanglement over a high-loss free-space channel
Alessandro Fedrizzi1, Rupert Ursin1, Thomas Herbst1, Matteo Nespoli1, Robert Prevedel1,2, Thomas Scheidl1, Felix Tiefenbacher1, Thomas Jennewein1 & Anton Zeilinger1,2
Quantum entanglement enables tasks not possible in classical physics. Many quantum communication protocols1 require the distribution of entangled states between distant parties. Here, we experimentally demonstrate the successful transmission of an entangled photon pair over a 144 km free-space link. The received entangled states have excellent, noise-limited fidelity, even though they are exposed to extreme attenuation dominated by turbulent atmospheric effects. The total channel loss of 64 dB corresponds to the estimated attenuation regime for a two-photon satellite communication scenario. We confirm that the received two-photon states are still highly entangled by violating the Clauser–Horne–Shimony–Holt inequality by more than five standard deviations. From a fundamental point of view, our results show that the photons are subject to virtually no decoherence during their 0.5-ms-long flight through air, which is encouraging for future worldwide quantum communication scenarios.
- Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria
- Quantum Optics, Quantum Nanophysics and Quantum Information, Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
Correspondence to: Alessandro Fedrizzi1 e-mail: alessandro.fedrizzi@univie.ac.at
Correspondence to: Anton Zeilinger1,2 e-mail: zeilinger-office@univie.ac.at
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