Metrological robustness of high photon number optical cat states

In the domain of quantum metrology cat states have demonstrated their utility despite their inherent fragility with respect to photon loss. 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 in the ideal case of vanishing losses, show almost twice the quantum Fisher information (QFI) compared to the even and odd cat states. However, and more importantly, these HHG-cat states are much more robust against noise such that the noisy HHG-cat outperforms the pure even/odd cat states even in the presence of more than $25\%$ losses in the regime of high photon numbers. Furthermore, in the regime of small losses, the HHG-cat remains almost pure while the even/odd cat state counterpart already decohere to the maximally mixed state. This demonstrates that high photon number optical cat states can indeed be used for metrological applications even in the presence of losses.Comment: 4 pages (3 figures