Alice & Bob's Interactive Stern-Gerlach Experiment

Magnetic field. Each magnet’s own field is the shared field in this page: the particle settles toward it, and its angle against the next magnet decides the flip.

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. This page uses the same half-cosine draw the medium-bound model uses, so a single particle through sequenced magnets cannot tell the two readings apart. 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.