[ExI] ghosts

[scerir]

... a beam is split, with part going to the object 
before hitting a photon-counting detector to capture 
light scattered from the object and part going 
an equal distance to a digital camera ... where 
the object began appearing after about a thousand 
coincident pairs of photons were recorded ...

the present experiment
http://focus.aps.org/story/v21/st14

Yanhua Shih et al.
A CCD array is placed facing a chaotic light source 
and gated by a photon counting detector that simply 
counts all randomly scattered and reflected
photons from an object. A "ghost" image of the object 
is then observed in the gated CCD. Differing from 
all published ghost-imaging experiments, this setup 
captures ghosts from scattered and reflected light 
of an object, instead of the transmitted ones. 
This new feature is not only useful for practical 
applications, but is also important fundamentally. 
It further explores the nonclassical interference 
nature of thermal light ghost imaging.

the best reviews on quantum imaging
and those past experiments with SPDC
sources and with thermal sources
http://arxiv.org/abs/0707.0268
http://arxiv.org/abs/0706.2097