The image above was captured by a quantum camera that was never pointed at the cats. Strange as it may seem this experiment may have practical applications in optical imaging:
In medicine, for instance, doctors might probe tissues using invisible wavelengths of light that won’t damage cells, while simultaneously using entangled visible light beams to create clear images of the tissues.
The NatGeo article does a good job of explaining how the experiment was conducted and why it worked as does this IEEE Spectrum article. But quantum entanglement is notoriously counter-intuitive so sometimes a simple analogy helps
Here’s another way to think about it: imagine I want to see an object, so I shine a flashlight on it. But I don’t look at the flashlight beam. Instead I shine a second light in the opposite direction, and that second flashlight shows me the object.