Adaptive quantum state estimation for two optical point sources

In classical optics, there is a well-known resolution limit called Rayleigh's curse in the separation of two incoherent optical sources in close proximity. Recently, Tsang et al. [Phys. Rev. X 6, 031033 (2016)] revealed that this difficulty may be circumvented in the framework of quantum theory. Following their work, various estimation methods have been proposed to overcome Rayleigh's curse, but none of them enables us to estimate the positions of two point sources simultaneously based on single-photon measurements with high accuracy. In this study, we propose a method to simultaneously estimate the positions of two point sources with the highest accuracy using an adaptive quantum state estimation scheme.