Fundamental resolution limit of quantum imaging with undetected photons

TL;DR

This paper theoretically establishes that quantum imaging with undetected photons is fundamentally limited by diffraction, with resolution constrained by the longer wavelength of the photon pairs, extending to other non-local two-photon imaging methods.

Contribution

It provides a general formalism beyond the paraxial approximation to prove the diffraction-limited resolution in undetected photon quantum imaging.

Findings

Resolution is limited by the longer wavelength of photon pairs.

The diffraction limit applies to various non-local two-photon imaging schemes.

The formalism extends beyond the paraxial approximation.

Abstract

Quantum imaging with undetected photons relies on the principle of induced coherence without induced emission and uses two sources of photon-pairs with a signal- and an idler photon. Each pair shares strong quantum correlations in both position and momentum, which allows to image an object illuminated with idler photons by just measuring signal photons that never interact with the object. In this work, we theoretically investigate the transverse resolution of this non-local imaging scheme through a general formalism that treats propagating photons beyond the commonly used paraxial approximation. We hereby prove that the resolution of quantum imaging with undetected photons is fundamentally diffraction limited to the longer wavelength of the signal and idler pairs. Moreover, we conclude that this result is also valid for other non-local two-photon imaging schemes.