In the quantum world, collisions don't destroy particles but weave them into an unbreakable knot: internal states and motions become entangled like threads. Scientists have developed a universal method to measure this entanglement directly from collision data.

Entanglement can be discrete (like knots on a rope), continuous (smooth loops), or hybrid — a multi-layered tangle reminiscent of Schrödinger's cat in a dozen boxes. To describe it, scientists used an approach proposed by John Wheeler for nuclear reactions.

Using spectroscopy of magnetic resonances, researchers showed that a weak magnetic field can turn entanglement on and off in ultracold collisions (such as rubidium with strontium fluoride). Even in an ordinary reaction of fluorine with hydrogen, the products are born entangled. Chemical reactions become factories of quantum knots for future technologies.