Editing Appendix/CGH/QuantumTransitions (section)

==Digital Holography==
When a ray of coherent, monochromatic light passes through a square aperture, a specific diffraction pattern is created.  The same result is achieved by bouncing the light off of one side of a cube [serving as the square aperture].  In this manner, information about a localized structure (the aperture) is preserved in a (diffraction) pattern that formally extends to infinity.  A hologram is created by "storing" the diffraction pattern (amplitude with no phase) as an image.

This process can be reversed.  A ray of coherent, monochromatic light that bounces off of (or shines through) the holographic image will &#8212; at the appropriate distance from the hologram &#8212; display an image of the original compact aperture.

Note that, either way &#8212; that is, whether the aperture is being used to create the diffraction pattern or ''vise versa'' &#8212; the diffraction pattern/hologram can be viewed as a probability distribution.