Detecting photons typically requires absorbing them. However, in some applications, a single photon may carry valuable information, such as data needed for a quantum computation. In such cases, scientists would like to read out the photon's data but also keep track of the photon as it travels in order to make sure it reaches its final destination successfully.
Regarding the motivation, is it satisfactory to absorb the photon, recording its state, and then re-emit a new one with those same properties? Is there a difference?
