Entangled quantum states provide novel ways for nonlocal imaging. Well known is ghost imaging where the image appears for a photon entangled with the one which interacts with the object. Most recently, it was seen that exploiting just the product state nature of photon pairs, one can obtain imaging where the photon interacting with the object does not even have to be detected.
In this lecture, I will discuss particularly the role of information in these imaging methods, and it will be shown that in some experiments, the photon interacting with the sample has to be detected in order to destroy path information and make imaging possible. In the more recent case, this is not necessary at all. It turns out that the phenomenon of “quantum imaging with undetected photons” exploits the fact that the phase of a product state cannot be localized. I will present practical applications and an outlook for future experiments.
