Generation of Continuous Variable Einstein-Podolsky-Rosen Entanglement via the Kerr Nonlinearity in an Optical Fiber

We report on the generation of a continuous variable Einstein-Podolsky-Rosen (EPR) entanglement using an optical fiber interferometer. The Kerr nonlinearity in the fiber is exploited for the generation of two independent squeezed beams. These interfere at a beam splitter and EPR entanglement is obtained between the output beams. The correlation of the amplitude (phase) quadratures is measured to be $4.0\pm 0.2$ $(4.0\pm 0.4)\mathrm{dB}$ below the quantum noise limit. The sum criterion for these squeezing variances $0.80\pm 0.03<2$ verifies the nonseparability of the state. The product of the inferred uncertainties for one beam $(0.64\pm 0.08)$ is well below the EPR limit of unity.