Correlated imaging, quantum and classical

TLDR

Classical beams are spatially correlated in both the near and far fields. The study demonstrates that classically correlated thermal beams can perform coherent imaging, closely matching the resolution, statistics, and imaging properties of entangled beams, suggesting entanglement is not essential for correlated imaging.

Abstract

We analytically show that it is possible to perform coherent imaging by using the classical correlation of two beams obtained by splitting incoherent thermal radiation. A formal analogy is demonstrated between two such classically correlated beams and two entangled beams produced by parametric down-conversion. Because of this analogy, the classical beams can mimic qualitatively all the imaging properties of the entangled beams, even in ways which up to now were not believed possible. A key feature is that these classical beams are spatially correlated both in the near field and in the far field. Using realistic numerical simulations the performances of a quasithermal and a parametric down-conversion source are shown to be closely similar, both for what concerns the resolution and statistical properties. The results of this paper provide a scenario for the discussion of what role the entanglement plays in correlated imaging.