  Ghost imaging has been used in archaeology, bio-medicine, for seeing through
turbid media, and promises X-ray imaging improvements, amongst many other
applications. However, the advantage of ghost imaging over regular imaging is
difficult to quantify. We searched for a simple example that can be quantified
with basic statistics. Using classical computational ghost imaging, we find
that the signal-to-noise ratio for ghost imaging of a slit (the object) can
exceed that of regular imaging with the same exposure of the slit when the
detectors are sufficiently noisy. This result is obtained by numerical
simulation and by theoretical analysis. We propose an experiment using a
spontaneous down-conversion source to demonstrate this quantitative imaging
advantage.
