understand whether quantum light can make visible the invisible.
This is a nice (and up-to-date) review of several aspects of quantum imaging.
Imaging is limited by «diffraction (due to light’s wave-like nature) and shot noise (related to light’s particle-like behaviour)»
Progress is fast:
On the difference/relationship of mode and quantum state:
the modal structure of a light beam24,25. These parameters, typically considered in imaging devices, do not change the quantum state but the underlying classical mode basis on which it is built. They encompass the spatial intensity distribution, frequency spectrum, polarization and even the phase of the light field. Measurement sensitivity in these situations directly depends on the chosen mode basis, and choosing it properly can induce a dramatic scaling change26.
They also point to spatial-mode demultiplexing (SPADE).
Bright squeezed light is increasingly applied in imaging and biological microscopy, improving the SNR and resolution