title: Demonstration of a quantum-enhanced fiber Sagnac interferometer.
abstract: The injection of squeezed light can be used to improve the sensitivity of an interferometer beyond the limit imposed by the zero-point fluctuation of the electromagnetic field. Here, we report on the realization of such a quantum-enhanced interferometer with a fiber-based Sagnac topology. Continuous wave squeezed states at 1550 nm with a noise reduction of 6.4 dB below shot noise were produced by type I optical parametric amplification and subsequently injected into the dark port of the interferometer. A reduction of the interferometer shot noise by 4.5 dB was observed, and the enhancement of the signal-to-noise ratio for a phase modulation signal generated within the interferometer could be demonstrated. We achieved a 95% fiber transmission for the squeezed states, which suggests that corresponding fiber-based quantum metrology and communication systems are feasible.
authors.affiliation: Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) and Institut für Gravitationsphysik derLeibniz Universität Hannover, Callinstrasse 38, 30167 Hannover, Germany.
authors.forename: Moritz
authors.initials: M
authors.lastname: Mehmet
authors.forename: Tobias
authors.initials: T
authors.lastname: Eberle
authors.forename: Sebastian
authors.initials: S
authors.lastname: Steinlechner
authors.forename: Henning
authors.initials: H
authors.lastname: Vahlbruch
authors.forename: Roman
authors.initials: R
authors.lastname: Schnabel