Abstract We propose a theoretical scheme of an enhanced phase sensitivity by introducing a nonlinear phase shifter to the nonconventional interferometer consisting of a balanced beam splitter (BBS) and an optical parameter amplifier (OPA), a modified nonlinear interferometer (MNI). Then we use coherent state and even coherent state as inputs and homodyne detection at one output port of the MNI for phase sensitivity, both without and with photon losses. We find that the nonlinear phase shifter can not only improve phase sensitivity, but also significantly resist the decoherence from photon losses. In comparison to both the BBS+OPA scheme with linear phase shifter and the traditional Mach–Zehnder interferometer with nonlinear one, the phase sensitivity of the MNI scheme shows the best performance. It is interesting that the nonlinear phase shifter can stimulate potential of the OPA, although there is no improvement in signal-to-noise ratio beyond standard quantum limit for the BBS+OPA scheme with a linear phase shifter.

中文翻译：

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使用非常规干涉仪和非线性移相器增强相位灵敏度

摘要 我们提出了一种通过将非线性移相器引入由平衡分束器 (BBS) 和光学参数放大器 (OPA) 组成的非常规干涉仪、改进的非线性干涉仪 (MNI) 来提高相位灵敏度的理论方案。然后我们使用相干态甚至相干态作为输入，并在 MNI 的一个输出端口进行零差检测，以获得相位灵敏度，无论有无光子损失。我们发现非线性移相器不仅可以提高相位灵敏度，还可以显着抵抗光子损失的退相干。与带有线性移相器的 BBS+OPA 方案和带有非线性移相器的传统 Mach-Zehnder 干涉仪相比，MNI 方案的相位灵敏度表现出最佳性能。