Generating Atomic Ghost Images

Although the phrase “ghost imaging” might sound like it involves photographing phantoms it is in fact a method of physical imaging otherwise I would be unlikely to write about it now. The basic concept is that an object can be photographed without the beam of particles that produce the photograph directly interacting with the object. To do this one beam of photons is sent to a high resolution multi pixel detector. The other beam of photons, split off from the same source, is aimed at the object being photographed behind which there is a single pixel plate detector known as a bucket. Thinking one pixel at a time makes it simpler to understand. If both the multi pixel and the bucket receive a signal at a particular pixel (and the corresponding location on the plate) then neither photon was blocked so the object was not covering this pixel. If the bucket receives no photons in a particular pixel coordinat then the object obscures this location and so an image can be formed despite the multi pixel photons never getting blocked. Since this is a quantum phenomenon it is not quite as simple as this and complex light distributions are actually used rather than single pixel illumination. What relation this has to quantum entanglement is still up for debate.

It has also been recently proven that this imaging techniques works with massive particles as well as photons. By getting two Bose-Einstein condensates and smashing them together correlated pairs of slow moving helium atoms were created which were then used to produce the same ghost images of objects. Although this may be impractical as an imaging technique it is still some very valuable information. This research can be developed to try and prove quantum entanglement and Bell’s inequality in relation to atoms rather than photons.


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