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We report the first measurement of the joint photon-number probability distribution for a two-mode quantum state created by a nondegenerate optical parametric amplifier. The measured distributions exhibit up to 1.9 dB of quantum correlation between the signal and idler photon numbers, whereas the marginal distributions are thermal as expected for parametric fluorescence.

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We used a spatially broadband optical parametric amplifier for image amplification. In the phasesensitive configuration of the amplifier, we observed noiseless amplification of input images. For a gain of Ӎ2.5, we measured noise-figure values of (0.2 6 0.6) and (0.4 6 0.5) dB, respectively, for two amplifiers of different lengths. These experimental values agree with theory (for an ideal noiseless amplifier the noise figure is 0 dB) and are almost 2 dB lower than the quantum limit of an ideal phaseinsensitive amplifier.