Enhancing Phase Sensitivity in Mach–Zehnder Interferometers for Arbitrary Input States
Hongbin Liang1, Jiancheng Pei1, and Xiaoguang Wang1,2*
1Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University, Hangzhou 310027, China 2Graduate School of China Academy of Engineering Physics, Beijing 100193, China
Abstract：To enhance the phase sensitivity of Mach–Zehnder interferometers, we use a tunable phase shift before the light beams are injected into the interferometer. The analytical result of the optimal phase shift is obtained, which only depends on the initial input states. For a non-zero optimal phase shift, the phase sensitivity of the interferometers in the output ports is always enhanced. We can achieve this enhancement for most states, including entangled and mixed states. The optimal phase shift is exhibited in three examples. Compared to previous methods, this scheme provides a general way to improve phase sensitivity and could find wide applications in optical phase estimations.
2020, Vol. 37 
