Metasurface-assisted photon-magnon conversion at ultralow temperatures for quantum computing technologies

The scalability of quantum computing systems based on superconducting qubits is limited by the low integration of quantum modules and the thermal load on cryogenic stages of refrigerators. A key element of scalable architectures is the microwave-magnon-optical (MMO) converter, which coherently connects microwave and optical circuits. We propose an approach to reducing the thermal load on the MMO converter using metasurface-based microwave structures with strong magnetic field localization. This design allows the main microwave circuitry to operate at higher refrigerator stages, leaving only the ferrimagnetic element at ultralow temperatures, thus improving overall scalability and thermal efficiency.