Super-resolution of two unbalanced point sources assisted by the entangled partner

Abstract

Sub-diffraction-limit resolution, or super-resolution, had been successfully demonstrated by recent theoretical and experimental studies for two-point sources with ideal equal-brightness and strict incoherenceness. Unfortunately, practical situations of either non-equal brightness (i.e., unbalancenss) or partial coherence are shown to have fatal effects on resolution precision. As a step toward resolving such issues, we consider both effects together by including an entangled partner of the two-point sources. Unexpectedly, it is found that the two negative effects can counter affect each other, thus permitting credible super-resolution, when the measurement is analyzed in the entangled partner's rotated basis. A least resolvable finite two-source separation is also identified analytically. Our result represents useful guidance towards the realization of super-resolution for practical point sources. The vector-structure analog of quantum and classical light sources also suggests that our analysis applies to both contexts.