Microwave-to-Optical Quantum Transduction Utilizing Antiferromagnetic Magnons in Antiferromagnets

The quantum transduction, or equivalently quantum frequency conversion, between microwave and optical photons is an essential quantum technology to realize scalable quantum computers with superconducting qubits. Due to the large frequency difference between microwave and optical ranges, the transduction needs to be done via intermediate bosonic modes or nonlinear processes. In this study, we focus on the transduction mediated by magnons. While previous studies have so far utilized the ferromagnetic magnons in ferromagnets, here we formulate a theory for the microwave-to-optical quantum transduction utilizing the antiferromagnetic magnons in antiferromagnets. We derive analytical expressions for the transduction efficiency in the cases with and without an optical cavity (where a microwave cavity is used in both cases). In contrast to the case of ferromagnets, we find that the quantum transduction can occur even in the absence of an external magnetic field. We also find that, in the case with an optical cavity, there exists an optimal value of the thickness d of the antiferromagnets at which the transduction efficiency takes a maximum value. This results from a competition between the microwave-magnon interaction ∝ √d and the light-magnon interaction ∝ 1 / √d.