Quantum sensing with nonclassical resources for SU(1, 1) interferometer

SU(1,1) interferometer, despite photon losses, significantly enhances the phase sensitivity and quantum Fisher information (QFI) which is a key metric for quantifying ultimate measurement precision in quantum systems. By applying non-Gaussian operations, like photon addition and subtraction within an SU(1,1) interferometer improves robustness against photon losses. However, implementing these non-Gaussian techniques comes with considerable challenges, as they involve high operational complexity and significant costs. We propose a novel method for enhancing phase estimation in the displacement-assisted SU(1,1) (DSU(1,1)) interferometer by incorporating the photon recycling technique, evaluated under single-intensity detection (SID) and homodyne detection (HD) schemes. Our analysis showed that utilizing the photon recycling technique, the photon-recycled DSU(1,1) interferometer performs better than the conventional DSU(1,1) interferometer under some conditions. We also showed that this improvement is possible in both SID and HD schemes. In addition, to discuss the maximum sensitivity achieved by our proposed model, we have calculated the quantum Cramér-Rao bound (QCRB) within the framework and found that our proposed model approaches the QCRB. This talk is based on our recent work [APL Quantum 2, 016127 (2025)].