Magnons, the quanta of spin waves, propagate in nanoscale magnetic structures and carry information in the form of spin angular momentum. They can be employed as data carriers in next-generation classical and quantum information processing systems. While recent years have seen significant breakthroughs in the development of unconventional magnonic circuits at room-temperature, the field of experimental quantum magnonics remains in its early stages. Currently, the main milestone is the excitation of a single magnon in the form of a non-propagating Kittel mode in a YIG sphere by entanglement with a superconducting (SC) qubit. However, this approach does not allow operations with spatially-separated propagating and entangled magnons.

In this project, we combine all the accumulated experience in the realisation of macro- and nanoscale magnonic circuits at room temperature with the knowledge in non-linear and parametric magnon physics, and with the recent achievements in magnon transport in YIG/GGG at millikelvin temperatures, to take a qualitative next step towards the realisation of quantum circuits operating with entangled propagating single magnons. The final aim is the realisation of groundbreaking quantum magnonic circuit demonstrators, showcasing the capability of magnons to act as controllable entanglement buses and gates between SC qubits. The successful realisation of these objectives will pave the way for developing novel solid-state computing systems that integrate quantum and unconventional computing approaches within one nanoscale chip.