  Quantum imaging with undetected photons (QIUP) is a unique method of image
acquisition where the photons illuminating the object are not detected. This
method relies on quantum interference and spatial correlations between the twin
photons to form an image. Here we present a detailed study of the resolution
limits of position correlation enabled QIUP. We establish a quantitative
relation between the spatial resolution and the twin photon position
correlation in the spontaneous parametric down-conversion process (SPDC).
Furthermore, we also quantitatively establish the roles that the wavelength of
the undetected illumination field and the wavelength of the detected field play
in the resolution. Like ghost imaging and unlike conventional imaging, the
resolution limit imposed by the spatial correlation between twin photons in
QIUP cannot be further improved by conventional optical techniques.
