Master equation approach to magnon relaxation and dephasing

TL;DR

This paper develops a quantum master equation framework to analyze magnon relaxation and dephasing, revealing distinct dissipation channels and their impact on quantum stability, crucial for quantum information applications involving magnons.

Contribution

It introduces a generalized master equation for magnon dynamics that accounts for local and collective dissipation, advancing understanding of magnon decoherence in quantum regimes.

Findings

Identifies local and collective dissipation channels for magnons.

Shows collective dissipation enhances quantum stability of squeezed magnons.

Provides a framework for studying magnon dephasing due to scattering and interactions.

Abstract

There has been a recent upsurge of interest in the quantum properties of magnons for quantum information processing. An important issue is to examine the stability of quantum states of magnons against various relaxation and dephasing channels. Since the interaction of magnons in magnetic systems may fall in the ultra-strong and even deep-strong coupling regimes, the relaxation process of magnon states is quite different from the more common quantum optical systems. Here we study the relaxation and dephasing of magnons based on the Lindblad formalism and derive a generalized master equation that describes the quantum dynamics of magnons. Employing this master equation, we identify two distinct dissipation channels for squeezed magnons, i.e., the local dissipation and collective dissipation, which play a role for both ferromagnets and antiferromagnets. The local dissipation is caused by the independent exchange of angular momentum between the magnonic system and the environment, while the collective dissipation is dressed by the parametric interactions of magnons and it enhances the quantumness and thermal stability of squeezed magnons. Further, we show how this formalism can be applied to study the pure dephasing of magnons caused by four-magnon scattering and magnon-phonon interactions. Our results provide the theoretical tools to study the decoherence of magnons within a full quantum-mechanical framework and further benefit the use of quantum states of magnons for information processing.