A new theory models loss in quantum magnonic resonators

Lars Meschede, Daniel D. A. Clarke, and Ortwin Hess of Trinity College Dublin have developed a new quantum theory to address a longstanding challenge in cavity quantum magnonics: consistently quantizing lossy gyrotropic resonators. Their work establishes a finite-temperature quantum quasinormal mode (QNM) theory, using macroscopic quantum electrodynamics and complex coordinate transformations for a wide range of dissipative magnonic systems. This approach allows for the quantitative design of hybrid quantum devices, integrating microwave photons, collective spin excitations, and superconducting or spin qubits within a single architecture, under realistic conditions, without relying on approximations. The researchers demonstrate the theory’s predictive power by modeling hybrid dielectric-magnonic resonators and observing effects like magnon-mediated qubit synchronization at both zero and finite temperatures. This theoretical framework accounts for spatially inhomogeneous, dissipative and dispersive characteristics within these systems, a step toward realizing the full potential of hybrid quantum devices. The new theory directly addresses the need for a quantized treatment of magnonic cavity resonances and their interaction…