I’d upvote you twice if I could!

….

It’s nice to get some recognition, thank you.

From the image caption:

Biphoton state holographic reconstruction. Image reconstruction. a, Coincidence image of interference between a reference SPDC state and a state obtained by a pump beam with the shape of a Ying and Yang symbol (shown in the inset). The inset scale is the same as in the main plot. b, Reconstructed amplitude and phase structure of the image imprinted on the unknown pump. Credit: Nature Photonics (2023). DOI: 10.1038/s41566-023-01272-3

Edit: Sounds like this is actually observed, but I don’t believe this is something one can “see”. The images are constructed from the difference between two states: one a reference state and the other being the state as captured by a pump. This isn’t all different, as I understand, than capturing light in film or a photo sensor: the reference state being the film/sensor detecting no light and the second state being when it exposed to light.

Searching “Cleveland Dam Secret Door” returned a Reddit post from a couple years ago. A commenter, who says they work for the local utility company, identified this as the “lower gallery portal” and it’s used for inspecting the dam.

Great photo!!