Now, researchers from Ghent University, the University of Cambridge and the University of Oxford may have found an answer. The researchers studied what happens when a quantum wave packet, representing a particle, meets a special boundary called a “duality defect.” In the 1980s, physicists Curtis Callan and Valery Rubakov studied what should happen when charged particles scatter from magnetic monopoles. The researchers also found that quantum entanglement—the deep connection between different parts of a quantum system—is central to the process. The defect contains its own hidden quantum state space, which determines how particles pass through it and what they become afterward.