Theoretical study on magnons in ferrimagnets and its application on quantum information processing

Abstract

In this thesis, we study the classical and the quantum characteristics of the magnons in the compensated ferrimagnets. We show that the compensated ferrimagnets can play a key role in the tasks of the quantum information process (QIP), such as the transformation of the quantum information or the generation of the quantum entanglement. We first investigate the coupling strength and the coupling frequency between the magnon and the photon. We find that the compensated ferrimagnets can have a strong couping strength and a high coupling frequency at the same time, which is not allowed for the antiferromagnets or the ferromagnets. We next study the entanglement between magnons in the compensated ferrimagnets. In contrast to the antiferromagnets, the compensated ferrimagnets can have the ground state that is arbitrarily close to the Einstein-Podolsky-Rosen (EPR) state. The ground-state entanglement diverges at the EPR state, and a large ground-state entanglement gives rise to a large steady-state entanglement. Consequently, the compensated ferrimagnet can have a larger steady-state entanglement compared to the antiferromagnet, especially in the vicinity of the EPR state. Thus, our work shows that the compensated ferrimagnet is a promising candidate as a new platform for performing the QIP tasks.