title: Continuous-wave nonclassical light with gigahertz squeezing bandwidth.
abstract: Squeezed states can be employed for entanglement-based continuous-variable quantum key distribution, where the secure key rate is proportional to the bandwidth of the squeezing. We produced a nonclassical cw laser field at the telecommunication wavelength of 1550 nm, which showed squeezing over a bandwidth of more than 2 GHz. The experimental setup used parametric downconversion via a periodically poled potassium titanyl phosphate crystal. We did not use any resonant enhancement for the fundamental wavelength, which should in principle allow a production of squeezed light over the full phase-matching bandwidth of several nanometers. We measured the squeezing to be up to 0.3 dB below the vacuum noise from 50 MHz to 2 GHz limited by the measuring bandwidth of the homodyne detector. The squeezing strength was possibly limited by thermal lensing inside the nonlinear crystal.
authors: Max-Planck-Institute for Gravitational Physics, Leibniz Universität Hannover, Callinstrasse 38, D-30167 Hannover, Germany.
authors: Stefan
authors: S
authors: Ast
authors: Aiko
authors: A
authors: Samblowski
authors: Moritz
authors: M
authors: Mehmet
authors: Sebastian
authors: S
authors: Steinlechner
authors: Tobias
authors: T
authors: Eberle
authors: Roman
authors: R
authors: Schnabel