Quantum SU(1,1) interferometers: Basic principles and applications

A new type of quantum interferometer was recently realized that employs parametric amplifiers (PAs) as the wave splitting and mixing elements. The quantum behavior stems from the PAs, which produce quantum entangled fields for probing the phase change signal in the interferometer. This type of quantum entangled interferometer exhibits some unique properties that are different from traditional beam splitter-based interferometers such as Mach–Zehnder interferometers. Because of these properties, it is superior to the traditional interferometers in many aspects, especially in the phase measurement sensitivity. We will review its unique properties and applications in quantum metrology and sensing, quantum information, and quantum state engineering.