Nonlinear phase estimation based on nonlinear interferometers with coherent and squeezed vacuum light

Abstract

Nonlinear interferometers, also known as SU(1,1) interferometers, are unconventional interferometers deploying nonlinear elements. Previous studies showed that they can provide better sensitivity than conventional Mach-Zehnder interferometers regarding the linear phase estimation. In this paper, we make use of nonlinear interferometers with coherent and squeezed vacuum states to perform nonlinear phase estimation. We discuss the optimal phase sensitivities in the absence and presence of photon losses. For a lossless environment, the optimal phase sensitivity can reach the Heisenberg limit scaling of 1/N2. Even with an internal lossy rate of 30% or an external lossy rate of 70%, our scheme can still achieve sub-shot-noise-limited phase sensitivity. These results indicate that our scheme is practical due to high sensitivity and strong robustness.