Unified Theory of Ghost Imaging with Gaussian-State Light

TL;DR

This paper develops a comprehensive Gaussian-state framework for ghost imaging, unifying classical and quantum theories, and identifies conditions under which nonclassical sources outperform classical ones in resolution and field-of-view.

Contribution

It introduces a complete Gaussian-state theory for ghost imaging, clarifying the classical-quantum boundary and demonstrating advantages of nonclassical sources.

Findings

Nonclassical Gaussian states improve resolution in near field.

Nonclassical Gaussian states enhance field-of-view in far field.

The image depends on phase-insensitive and phase-sensitive cross-correlations.

Abstract

The theory of ghost imaging is developed in a Gaussian-state framework that both encompasses prior work - on thermal-state and biphoton-state imagers - and provides a complete understanding of the boundary between classical and quantum behavior in such systems. The core of this analysis is the expression derived for the photocurrent-correlation image obtained using a general Gaussian-state source. This image is expressed in terms of the phase-insensitive and phase-sensitive cross-correlations between the two detected fields, plus a background. Because any pair of cross-correlations is obtainable with classical Gaussian states, the image does not carry a quantum signature per se. However, if the image characteristics of classical and nonclassical Gaussian-state sources with identical auto-correlation functions are compared, the nonclassical source provides resolution improvement in its near field and field-of-view improvement in its far field.