SPIN WAVES COUPLED TO A SUPERCONDUCTING CIRCUIT CREATE A ONE-WAY STREET FOR MICROWAVE SIGNALS

Summary from the TLDR Hardware newsletter

Argonne and UIUC researchers coupled spin waves in a thin yttrium iron garnet film to a superconducting resonator built directly on top, creating a hybrid mode that propagates one way and could keep return noise from leaking back into qubits. The key materials fix was swapping the usual rare-earth-containing substrate, which absorbs microwaves at low temperatures, for one without rare-earth metals. It's still a proof of concept.