It is commonly accepted that a parametric amplifier can simulate a phase-preserving linear amplifier regardless of how the latter is realized [C. M. Caves et al., Phys. Rev. A 86, 063802 (2012)]. If true, this reduces all phase-preserving linear amplifiers to a single familiar model. Here we disprove this claim by constructing two counterexamples. A detailed discussion of the physics of our counterexamples is provided. It is shown that a Heisenberg-picture analysis facilitates a microscopic explanation of the physics. This also resolves a question about the nature of amplifier-added noise in degenerate two-photon amplification.

中文翻译：

---

参数放大器无法模拟的保相线性放大器

公认的是，参数放大器可以模拟相位保持线性放大器，而不管其如何实现[C. M. Caves等。，物理 修订版A 86，063802（2012）]。如果为真，则将所有保相线性放大器简化为一个熟悉的模型。在这里，我们通过构造两个反例来证明这一主张。提供了关于我们的反例的物理学的详细讨论。结果表明，海森堡图像分析有助于对物理学进行微观解释。这也解决了关于简并双光子放大中放大器增加的噪声的性质的问题。