An actively correlated Mach-Zehnder interferometer (ACMZI) renders a number of significant advantages over a conventional Mach-Zehnder interferometer (MZI) with a squeezed vacuum state input such as an active output readout, loss tolerant detection, and multiarms for multiparameter estimation. We theoretically studied the quantum Cramér-Rao bound of an ACMZI, where the quantum Fisher information obtained by the phase-averaging method can give the conclusive phase-sensing sensitivity without any external phase reference. We numerically calculate the phase sensitivities with the method of homodyne detection and intensity detection in the presence of losses. Under lossless and very low loss conditions, the ACMZI is operated in a balanced case to beat the standard quantum limit (SQL). As the loss increases, the reduction in sensitivity increases. Fortunately, within a certain range, we can adjust the gain parameters of the beam recombination process to reduce the reduction in sensitivity and realize the sensitivity can continue to beat the SQL in an unbalanced situation. Our scheme provides an optimization method of phase estimation in the presence of losses.

中文翻译：

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损耗对主动关联 Mach-Zehnder 干涉仪灵敏度的影响

主动相关的 Mach-Zehnder 干涉仪 (ACMZI) 与具有压缩真空状态输入的传统 Mach-Zehnder 干涉仪 (MZI) 相比具有许多显着优势，例如有源输出读数、容错检测和用于多参数估计的多臂。我们从理论上研究了 ACMZI 的量子 Cramér-Rao 界，其中通过相位平均方法获得的量子 Fisher 信息可以在没有任何外部相位参考的情况下给出确凿的相位传感灵敏度。我们用零差检测和强度检测的方法在存在损耗的情况下数值计算相位灵敏度。在无损和极低损耗条件下，ACMZI 在平衡情况下运行以击败标准量子限制 (SQL)。随着损耗的增加，灵敏度的降低也会增加。幸运的是，在一定范围内，我们可以通过调整beam recombination过程的增益参数来减少灵敏度的降低，实现灵敏度在不平衡的情况下可以继续击败SQL。我们的方案提供了一种在存在损失的情况下相位估计的优化方法。