Microwave-to-Optics Conversion Using Magnetostatic Modes and a Tunable Optical Cavity

Quantum computing, quantum communication, and quantum networks rely on hybrid quantum systems operating in different frequency ranges. For instance, the superconducting qubits work in the gigahertz range, while the optical photons used in communication are in the range of hundreds of terahertz. Due to the large frequency mismatch, achieving the direct coupling and information exchange between different information carriers is generally difficult. Accordingly, a quantum interface is demanded, which serves as a bridge to establish information linkage between different quantum systems operating at distinct frequencies. Recently, the magnon mode in ferromagnetic spin systems has received significant attention. While the inherent weak optomagnonic coupling strength restricts the microwave-to-optical photon conversion efficiency using magnons, the versatility of the magnon modes, together with their readily achievable strong coupling with other quantum systems, endow them with many distinct advantages. Here, the magnon-based microwave-light interface is realized by adopting an optical cavity with adjustable free spectrum range and different kinds of magnetostatic modes in two microwave cavity configurations. By optimizing the parameters, a conversion efficiency of $1.75\times {10}^{-8}$ with bandwidth of 24 MHz is achieved. The impact of various parameters on the microwave-to-optics conversion is analyzed. The study provides useful guidance and insights to further enhancing the microwave-to-optics conversion efficiency using magnons.