Non-Classical Bistability And Tripartite Entanglement In Cavity Magnonic System

Cavity magnonics deals with the interaction of magnons(i.e.,elementary excitations in magnetic materials)and confined electromagnetic fields,and serves as the basis of almost all hybrid systems based on magnonics.Indeed,the magnetic dipole interaction between magnetostatic modes and microwave cavity modes is used in both quantum magnonics and cavity magnomechanics to engineer interactions with modes of physically distinct systems.Here,we introduce the basic magnonics and review the theoretical progress of this young field.In fact,the field is gearing up for integration in future quantum technologies.Most of its appeal is derived from the strong magnon-photon coupling and the easily-reached nonlinear regime in microwave cavities.The cavity photon-mediated coupling of a magnon mode to a superconducting qubit enables measurements in the single magnon limit.Therefore,the progress of cavity magnonics is the key cornerstone of constructing superconducting circuit hybrid system.In addition,we demonstrate how magnon Kerr nonlinearity creates bistability of quantum states when the magnon mode is strongly driven by a microwave field in a nonlinear cavity magnonic system.Numerical simulation results with experimentally feasible parameters show that the method,where the system is driven far from equilibrium is a reliable way to achieve squeezed states for magnons and photons and to carry out magnon-photon entanglement,and reveal mysterious phenomena of bistability.In addition,the Kittel mode can jump from one state to another one near two switching points,thus achieving the quantum state hysteresis loop phenomenon.Our results indicate that bistable quantum states could provide a way to study macroscopic quantum bistable phenomena in nonlinear systems and also can be found in broad applications in magnetic spintronics.In addition,we also present a method to enhance steady-state bipartite and tripartite entanglement in a cavity magnonics system by utilizing the Kerr nonlinearity.The system comprises two microwave cavities and a magnon and represents the collective motion of several spins in a macroscopic ferrimagnet.We prove that Kerr nonlinearity is reliable for the enhancement of entanglement and produces a small frequency shift in the optimal detuning.Our system is more robust against the environment-induced decoherence than traditional optomechanical systems.Finally,we briefly analyze the validity of the system and demonstrate its feasibility for detecting the generated entanglement.