Masaya Hiraishi

Masaya investigates microwave and optical transition properties of rare-earth ions in antiferromagnetic crystals. The motivation for this work is to realise a microwave-to-optical frequency conversion based on rare-earth ions in magnetically ordered crystals, which was theoretically proposed recently. This is a combined approach, merging two well-studied approaches: ensembles of rare-earth ions in non-magnetic crystals and collective excitations of spins, known as magnons, in magnetically ordered crystals. The rare-earth ions in non-magnetic crystals exhibit narrow optical linewidths with high optical densities. Magnons can strongly couple to an external microwave resonator mode due to the large number of spins involved in the magnon excitation. Therefore, he expects the rare-earth-magnon approach to exhibit narrow linewidths that can very strongly couple external cavity modes. Such a system will be an important building block for modular quantum computers composed of distant superconducting qubits which operate within a microwave frequency regime and are entangled with each other by optical photons.