title: Implementation of a nondeterministic optical noiseless amplifier.
abstract: Quantum mechanics imposes that any amplifier that works independently on the phase of the input signal has to introduce some excess noise. The impossibility of such a noiseless amplifier is rooted in the unitarity and linearity of quantum evolution. A possible way to circumvent this limitation is to interrupt such evolution via a measurement, providing a random outcome able to herald a successful-and noiseless-amplification event. Here we show a successful realization of such an approach; we perform a full characterization of an amplified coherent state using quantum homodyne tomography, and observe a strong heralded amplification, with about a 6 dB gain and a noise level significantly smaller than the minimal allowed for any ordinary phase-independent device.
authors.affiliation: Groupe d'Optique Quantique, Laboratoire Charles Fabry, Institut d'Optique, CNRS, Université Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau cedex, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Ferreyrol
authors.forename: Marco
authors.initials: M
authors.lastname: Barbieri
authors.forename: Rémi
authors.initials: R
authors.lastname: Blandino
authors.forename: Simon
authors.initials: S
authors.lastname: Fossier
authors.forename: Rosa
authors.initials: R
authors.lastname: Tualle-Brouri
authors.forename: Philippe
authors.initials: P
authors.lastname: Grangier