Entanglement ...

Engtanglement has never been photographed until now. Bell was right all along. :)

Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated, interact, or share spatial proximity in ways such that the quantum state of each particle cannot be described independently of the state of the others, even when the particles are separated by a large distance.

Spontaneous parametric down-conversion process can split photons into type II photon pairs with mutually perpendicular polarization.

Click here for more blurbs on entanglement & quantum theory if you dare. :)

Addendum: One more pix and info from Physorg.

Full-frame images recording the violation of a Bell inequality in four images. (A) The four coincidence counting images are presented, which correspond to images of the phase circle acquired with the four phase filters with different orientations, θ2 = {0° , 45° , 90° , 135°}, necessary to perform the Bell test. Scale bars, 1 mm (in the plane of the object). (B to E) The coincidence counts graphs as a function of the orientation angle θ1 of the phase step along the object are presented. As shown, these results are obtained by unfolding the ROIs represented as red rings and are extracted from the images presented in (A). The blue dots in the graphs are the coincidence counts per angular region within the ROIs, and the red curves correspond to the best fits of the experimental data by a cosine-squared function. (B) to (E) correspond to phase filter orientations θ2 of 0°, 45°, 90°, and 135°, respectively. Credit: Science Advances (2019). DOI: 10.1126/sciadv.aaw2563

For the first time ever, physicists have managed to take a photo of a strong form of quantum entanglement called Bell entanglement—capturing visual evidence of an elusive phenomenon which a baffled Albert Einstein once called 'spooky action at a distance'.

Two particles which interact with each other—like two photons passing through a beam splitter, for example—can sometimes remain connected, instantaneously sharing their physical states no matter how great the distance which separates them. This connection is known as quantum entanglement, and it underpins the field of quantum mechanics.

How cool is this? :)