Strong low-frequency quantum correlations from a four-wave mixing amplifier

摘要

We show that a simple scheme based on nondegenerate four-wave mixing in a hotatomic vapor behaves like a near-perfect phase-insensitive optical amplifier,which can generate bright twin beams with a measured quantum noise reduction inthe intensity difference of more than 8 dB, close to the best opticalparametric amplifiers and oscillators. The absence of a cavity makes the systemimmune to external perturbations, and the strong quantum noise reduction isobserved over a large frequency range.