In the emerging field of magnon spintronics, researchers seek to transport and process information by means of so-called magnon spin currents. In contrast to electrical currents, on which todays information technology is based, magnon spin currents conduct magnetic momenta. These are mediated by magnetic waves, or magnons, which propagate through magnetic materials. One fundamental building block of magnon spintronics is magnon logic, by which logic operations are processed by the superposition of spin currents.