title: Experimental error filtration for quantum communication over highly noisy channels.
abstract: Error filtration is a method for encoding the quantum state of a single particle into a higher dimensional Hilbert space in such a way that it becomes less sensitive to noise. We have realized a fiber optics demonstration of this method and illustrated its potentialities by carrying out the optical part of a quantum key distribution scheme over a line whose phase noise is too high for a standard implementation of BB84 to be secure. By filtering out the noise, a bit error rate of 15.3% +/- 0.1%, which is beyond the security limit, can be reduced to 10.6% +/- 0.1%, thereby guaranteeing the cryptographic security.
authors.affiliation: Quantum Information and Communication, Ecole Polytechnique, CP 165/59, Université Libre de Bruxelles, Avenue F. D. Roosevelt 50, 1050 Brussels, Belgium.
authors.forename: L-P
authors.initials: LP
authors.lastname: Lamoureux
authors.forename: E
authors.initials: E
authors.lastname: Brainis
authors.forename: N J
authors.initials: NJ
authors.lastname: Cerf
authors.forename: Ph
authors.initials: P
authors.lastname: Emplit
authors.forename: M
authors.initials: M
authors.lastname: Haelterman
authors.forename: S
authors.initials: S
authors.lastname: Massar