Imaging spin-wave propagation and interference with electron spins in diamond

The coherent transport of spin information in magnetic insulators is not associated with the heat dissipation of electronic currents. Therefore, it is envisioned that the next generation of information-processing devices could be based on spin waves, the elementary excitations of magnets that can reach nanometer wavelengths and terahertz frequencies. Here we use electron spins in diamond to probe coherent spin-wave transport in the magnetic insulator yttrium-iron-garnet (YIG). We image propagating spin-waves and their interference, we extract the dispersion relation, demonstrate time-domain control and quantify the magnetization oscillations carried by these excitations. These results pave the way for fundamental studies of spin-wave transport and to harness spin-wave interference in magnonic devices.