The History of HopfionsHopfions are three-dimensional topological structures defined by their unique geometry, instead of the material from which they are made. Developing hopfion crystals could lead to the creation of photonic devices that are less susceptible to interference. Scaling into Three DimensionsThe team suggested building three-dimensional hopfion crystals by arranging small emitters, such as microwave and dipole antennas, or grating couplers, with a set phase and polarization. Potential ApplicationsIf space-time hopfion crystals can be made in practice, they could impact fields such as optical communications, quantum computing, neuromorphic computing, and aerospace. The authors refer to their work as “the birth of space-time hopfion crystals”, highlighting its significance as a first step toward creating stable, repeating topological structures at optical, terahertz, and microwave frequencies.