In the domain of quantum metrology, cat states have demonstrated their utility despite their inherent fragility with respect to losses. Here, we introduce noise robust optical cat states which exhibit a metrological robustness for phase estimation in the regime of high photon numbers. These cat states are obtained from the intense laser driven process of high harmonic generation (HHG), and show a resilience against photon losses. Focusing on a realistic scenario including experimental imperfections we opt for the case in which we can maximize the lower bound of the quantum Fisher information (QFI) instead of analyzing the best case scenario. We show that the decrease of the QFI in the lossy case is suppressed for the HHG-cat state compared to the even and odd counterparts. In the regime of small losses of just a single photon, the HHG-cat state remains almost pure while the even/odd cat state counterparts rapidly decohere to the maximally mixed state. More importantly, this translates to a significantly enhanced robustness for the HHG-cat against photon loss, demonstrating that high photon number optical cat states can indeed be used for metrological applications even in the presence of losses.

中文翻译：

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高光子数光猫态的计量鲁棒性


在量子计量领域，猫态已经证明了它们的实用性，尽管它们在损耗方面具有固有的脆弱性。在这里，我们引入了抗噪光学猫态，它在高光子数状态下表现出相位估计的计量鲁棒性。这些猫态是从强激光驱动的高次谐波产生 (HHG) 过程中获得的，并且表现出对光子损失的恢复能力。着眼于包括实验缺陷在内的现实场景，我们选择可以最大化量子费希尔信息 (QFI) 下限的情况，而不是分析最佳情况。我们表明，与偶数和奇数对应物相比，HHG-cat 状态在有损情况下 QFI 的下降受到抑制。在仅单个光子的小损失的情况下，HHG-cat 状态几乎保持纯净，而偶/奇猫状态对应物迅速退相干到最大混合状态。更重要的是，这意味着 HHG-cat 对抗光子损失的稳健性显着增强，表明即使存在损失，高光子数光学猫状态确实可以用于计量应用。