Quantum entangled Sagnac interferometer

Abstract

A SU(1,1) interferometer (SUI) is a kind of quantum entangled interferometer that uses directly entangled quantum fields for sensing phase change. For rotational sensing, Sagnac geometry is usually adopted. However, because SUI depends on the phase sum of the two arms, traditional Sagnac geometry, when applied to SUI, will result in null signal. In this paper, we modify the traditional Sagnac interferometer by nesting SUIs inside. We show that the rotational signal comes from two parts labeled as “classical” and “quantum,” respectively, and the quantum part, where quantum entangled fields are used for sensing, has the rotational signal enhanced by a factor related to the gain of the SUI.