Object Imaged with Light that Never Touched It
Whenever you take a picture, the photons that are captured were actually reflected or scattered by the objects in the image. This is how cameras have always worked, but could it be possible to take a picture with photons that never interacted with the imaged object? It must be as researchers at the University of Vienna, Institute for Quantum Optics and Quantum Information, and the Vienna Center for Quantum Science and Technology have done so.
To achieve this seemingly impossible task, the researchers turned to quantum mechanics and the phenomenon entanglement in particular. Entanglement is when particles are so tightly bound together that the properties of one can affect and determine properties of the other, even when separated over great distances. To create the entangled particles, the researchers fired a laser into a pair of nonlinear crystals, with the imaged object in the middle. Both crystals created pairs of entangled photons, but one would be an infrared photon while the other would just be red. The optics of the experiment made sure all of the infrared photons from the first crystal took the path that would have them interact with the target, a sketch of a cat, while the red photons would remain clear of it. The infrared photons would then enter the second crystal, combining with any infrared photons made there. All of these infrared photons were then discarded, while the red photons were captured by a camera that could not even see the infrared photons.
Despite the red photons never interacting with the sketch of the cat, the beams still recreated it in bright and dark patterns, because the information of the infrared photons was preserved by the red photons. This research could see some very interesting applications in the future, including in medical and biological imaging where low light imaging is important.
Source: University of Vienna