Messung und graphische Darstellung von Ein- und Zwei-Moden-gequetschten Zuständen des Lichts

Abstract

The standard process for the production of strongly squeezed states of light is degenerate optical parametric amplification (OPA) below threshold in nonlinear dielectric media such as lithium niobate or periodically poled potassium titanyl phosphate.This work presents the generation of the most strongly squeezed states of light so far, as well as the first graphical description of squeezed-light generation via OPA.The newly developed graphical description visualizes the interaction between the nonlinear dielectric polarization of the medium and the electromagnetic quantum field.It explicitly focuses on the transition from the field's ground state to a squeezed vacuum state, and from a coherent state to a bright squeezed state by the medium's second-order nonlinearity.The pictures visualize the phase-dependent amplification and deamplification of quantum uncertainties, and give the phase relations between all propagating electromagnetic fields, as well as the internally induced dielectric polarizations.The graphical description can also be used to describe the generation of nonclassical states of light via higher-order effects of the nonlinear dielectric polarization, such as four-wave mixing, and the optical Kerr effect.By superposing strongly squeezed states of light, strongly entangled states can be produced.This work measured states such as those discussed in 1935 in the famous gedanken experiment by Einstein, Podolsky and Rosen (EPR) and introduced by Schrödinger in terms of entanglement and steering.The source of entanglement in this work was composed of a half-monolithic, optically nonlinear cavity providing 11,3 dB squeezing and a monolithic, optically nonlinear cavity providing 12,7 dB squeezing.The latter value is the highest noise suppression up to now.This source of entanglement achieved a sixfold increase of the observed EPR-steering effect with regard to previous experiments, as quantified by the Reid criterion.It achieved an unprecedentedly low conditional variance product of about 0,04 < 1, where 1 is the upper bound below which steering is demonstrated.The steering effect was observed on an unconditional two-mode-squeezed entangled state that contained a total vacuum state contribution of less than 8 %, including detection imperfections.Together with the achieved high interference contrast between the entangled state and a bright coherent laser field, this state is compatible with efficient applications in high-power laser interferometers and fiber-based networks for entanglement distribution.