Lens-less quantum ghost imaging: New two-photon experiments

New types of lens-less two-photon ghost imaging experiments are described that can also be useful for 3D X-ray imaging. In these experimental setups, a CCD array is placed facing a chaotic light source and gated by a photon counting detector that simply counts all randomly reflected photons from an object. A “ghost” image of the object is then observed from the gated CCD. A ghost image of an object can even be observed when the photon path to the photon counting device is obscured. These interesting demonstrations are not only useful for practical applications, such as X-ray lens-less imaging, but are also important from a fundamental point of view. These demonstrations lead to insight regarding the nonclassical two-photon interference nature of thermal light ghost imaging.