Alice & Bob's Interactive Particle Mechanism Experiment

Magnetic field. The Stern-Gerlach magnet’s field is the shared field here: it turns the particle’s reference frame and pulls its angle toward the magnet’s own.

Medium-bound. The same shared value can come from the medium the particle sits in. One of the two is the primary (the one whose start angle is nearest the pair’s hidden plane, fixed at emission), it sets the reference, and the other follows it. (+) is expanded space and (−) is compressed space. With one particle and one magnet this page cannot tell the two readings apart. Both turn the frame and give the same flips; they are equally plausible.

Photon splitters. We have not studied beam-splitter experiments yet. The same story may carry over, with the splitter playing the part of the magnet. This is a suggestion only, not tested.