1998/06/12 by W. Tittel, J. Brendel, H. Zbinden +1 · 3 citations
Physics and Astronomy · #quant-ph
paper · pdf · doi:10.1103/physrevlett.81.3563
published as Phys.Rev.Lett. 81 (1998) 3563-3566 · 4 pages, REVTeX, 2 postscript figures included
arxiv created 1998/06/12 · arxiv updated 2009/12/01
A Franson-type test of Bell inequalities by photons 10.9 km apart is presented. Energy-time entangled photon-pairs are measured using two-channel analyzers, leading to a violation of the inequalities by 16 standard deviations without subtracting accidental coincidences. Subtracting them, a 2-photon interference visibility of 95.5% is observed, demonstrating that distances up to 10 km have no significant effect on entanglement. This sets quantum cryptography with photon pairs as a practical competitor to the schemes based on weak pulses.