Quantum enhancement of phase sensitivity for SU(1,1) interferometer via low-noise boost of phase sensing photons using non-Gaussianity

We propose to utilize photon-addition-then-subtraction (PATS) scheme to enhance the phase sensitivity of SU(1,1) interferometer (SUI). By performing PATSs on the internal arms of the SUI, we demonstrate that the phase sensing photon number (PSPN) inside the interferometer can be increased efficiently. The extra noise addition caused by such PSPN boost is very low. It is the low-noise boost of the PSPN that leads to the quantum enhancement of the PATS-based SUI. We demonstrate that the PATS scheme can improve the robustness of the SUI against internal loss of the interferometer, which is one of the main limitations degrades the performance of the standard SUI. In addition, we also find that the PATS-based SUI is capable of mitigating the saturation effect of the detector, when the input of the interferometer is small.