spin excitations - magnons (spin wave quanta) - open up a very promising
direction. Magnons are bosons, and thus they are able to form spontaneously a
spatially extended, coherent ground state, a Bose-Einstein condensate (BEC).
The BEC can be conveniently created in a single-crystal film of yttrium iron
garnet even at room temperature using parametric pumping. An extraordinary
challenge is the use of this macroscopic quantum state for information transfer
and processing. Recently we have succeeded to create a magnon supercurrent in
such a macroscopic quantum state. I will present new, non-locally measured
evidence for these supercurrents, discuss their properties, and I will provide
an outlook toward potential future applications.