Violation of Bell Inequalities by Photons More Than 10 km Apart
Abstract
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 two-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.
- Publication:
-
Physical Review Letters
- Pub Date:
- October 1998
- DOI:
- 10.1103/PhysRevLett.81.3563
- arXiv:
- arXiv:quant-ph/9806043
- Bibcode:
- 1998PhRvL..81.3563T
- Keywords:
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- Quantum Physics
- E-Print:
- 4 pages, REVTeX, 2 postscript figures included