Optical interferometer using two-mode squeezed light for enhanced chip-integrated quantum metrology

This paper discusses the possibility of using two-mode squeezed light to improve the performance of existing sensor technology with the focus on its miniaturization under realistic losses. Therefore, we analyze a system consisting of a part for two-mode squeezed light generation, a sensor region, and a detection stage. Based on a general four-wave mixing (FWM) Hamiltonian caused by third-order susceptibility, we formulate linearized equations that describe the FWM process below the threshold and are used to analyze the squeezing quality of the generated optical signal and idler modes. For a possible realization, the focus is set on chip-integrated generation using microring resonators. To do so, the impacts of the design and the pump light are considered in the derived equations. These equations are used to analyze the usage of two-mode squeezed light in quantum metrology and the application in a Mach-Zehnder interferometer. Due to the impact of losses in realistic use cases, we show that the main usage is for small and compact devices, which can lead to a quantum improvement of up to a factor of 10 in comparison with using coherent light only. This enables the use of small squeezing-enhanced sensors with a performance comparable to larger classical sensors.