Phase-sensitive optical parametric amplification of squeezed states helps to overcome detection loss and noise and thus increases the robustness of sub-shot-noise sensing. Because such techniques, e.g., imaging and spectroscopy, operate with multimode light, multimode amplification is required. Here we find the optimal methods for multimode phase-sensitive amplification and verify them in an experiment where a pumped second-order nonlinear crystal is seeded with a Gaussian coherent beam. Phase-sensitive amplification is obtained by tightly focusing the seed into the crystal, rather than seeding with close-to-plane waves. This suggests that phase-sensitive amplification of sub-shot-noise images should be performed in the near field. A similar recipe can be formulated for the time and frequency, which makes this work relevant for quantum-enhanced spectroscopy.

中文翻译：

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相敏状态下的多模光学参量放大

压缩态的相敏光参量放大有助于克服检测损失和噪声，从而提高子散粒噪声感测的鲁棒性。因为这样的技术，例如成像和光谱学，在多模光下工作，所以需要多模放大。在这里，我们找到了用于多模相敏放大的最佳方法，并在一个实验中进行了验证，在该实验中，泵浦的二阶非线性晶体被高斯相干光束注入。通过将晶种紧密地聚焦在晶体中，而不是使用近平面波进行晶种，可以获得相敏放大。这表明应该在近场中对子散粒噪声图像进行相敏放大。可以为时间和频率制定类似的配方，