We present a method to enhance steady-state bipartite and tripartite entanglement in a cavity-optomagnonics system by utilizing the Kerr nonlinearity originating from the magnetocrystalline anisotropy. 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.
We present a method to enhance steady-state bipartite and tripartite entanglement in a cavity-optomagnonics system by utilizing the Kerr nonlinearity originating from the magnetocrystalline anisotropy. 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.
We propose a hybrid cavity-magnon optomechanical system with mechanical nonlinearity to enhance both bipartite and tripartite entanglement. This system comprises a microwave cavity QED, a YIG sphere, and a mechanical oscillator. Our results demonstrate a significant enhancement of both bipartite and tripartite entanglement through the utilization of mechanical nonlinearity. Moreover, the entanglement prepared by this system exhibits better temperature robustness compared to the traditional system. Finally, we conduct thorough physical calculations to analyze in detail the mechanisms by which mechanical nonlinearity enhances entanglement. Additionally, we determine the position within the system that yields the maximum bipartite entanglement through calculations.
Abstract We propose a scheme to generate squeezed states in a cross-shaped cavity magnonics system by Kerr effect originating from the magnetocrystalline anisotropy. The system consists of two microwave cavities and a yttrium iron garnet sphere supporting a magnon mode embodying the collective spin motion, and each cavity mode is coupled with the magnon mode through the magnetic-dipole interaction. It is demonstrated that simultaneous squeezing of the two microwave cavity modes and the magnon mode can be achieved due to Kerr nonlinearity, and the squeezing of the magnon mode can break the 3 dB limit. By utilizing a Bogoliubov transformation, a new perspective on the underlying physical mechanism for the generation of the squeezing using Kerr nonlinearity is provided. Moreover, we also demonstrate the strong robustness of the magnon mode’s squeezing against the system dissipation and environmental temperature. The present scheme provides a promising platform for quantum information processing, holding significant implications for quantum metrology and precision measurement.
Quantum illumination is a quantum optical sensing technique, which employs an entangled source to detect low-reflectivity object immersed in a bright thermal background. Hybrid cavity-optomagnonics system promises to work as quantum illumination because a yttrium iron garnet (YIG) sphere can couple to microwave field and optical field. In this paper, we propose a scheme to enhance the entanglement between the output fields of the microwave and optical cavities by considering the intrinsic Kerr nonlinearity of the YIG. We investigate the difference between intrinsic Kerr nonlinearity and optomagnonical parametric-type coupling on improving entanglement. Our result show that the large value optomagnonical parametric-type coupling does not mean the large entanglement, nevertheless, the large value of Kerr nonlinearity does monotonously improve the entanglement for our group of parameters. Consequently, under feasible parameters of current experiment, the signal-to-noise ratio and probability of detection error can be improved after considering the magnon Kerr nonlinearity.
Cavity optomechanics, a promising platform to investigate macroscopic quantum effects, has been widely used to study nonreciprocal entanglement with the Sagnac effect. Here, we propose an alternative way to realize nonreciprocal entanglement among magnons, photons, and phonons in a hybrid cavity-magnon optomechanics, where the magnon Kerr effect is used. We show that the Kerr effect gives rise to a magnon frequency shift and an additional two-magnon effect. Both of them can be tuned from positive to negative via tuning the magnetic field direction, leading to nonreciprocity. By tuning system parameters such as magnon frequency detuning or the coefficient of the two-magnon effect, bipartite and tripartite entanglements can be nonreciprocally enhanced. By further studying the defined bidirectional contrast ratio, we find that nonreciprocity in our system can be switched on and off, and can be engineered by the bath temperature. Our proposal not only provides a potential path to demonstrate nonreciprocal entanglement with the magnon Kerr effect, but also opens a direction to engineer and design diverse nonreciprocal devices in hybrid cavity-magnon optomechanics with nonlinear effects.
Abstract We propose a scheme to generate steady-state bipartite and tripartite entanglement in the cavity magnomechanical system, which consists of a microwave (MW) cavity field, three magnons, and a phonon mode. The three magnons are coupled to the MW cavity via the magnetic dipole interaction, and one of them is also coupled to the phonon mode through the magnetostrictive force. By utilizing the nonlinearity of the magnetostrictive force and the cavity-magnon interaction, the three magnons become mutually entangled, and the steady-state of the system displays a genuine tripartite entanglement. We found that there are optimum parameters, including the detunings and the cavity-magnon coupling, which lead to maximum entanglement. Moreover, the entanglement is robust against thermal effects.
Quantum entanglement will play an important role in future quantum technologies. Here, we theoretically study the steady-state entanglement between a cavity field and a macroscopic rotating mirror in a Laguerre–Gaussian-(LG)-cavity optomechanical system with cross-Kerr nonlinearity. Logarithmic negativity is used to quantify the steady-state entanglement between the cavity and mechanical modes. We analyze the impacts of the cross-Kerr coupling strength, the cavity detuning, the input laser power, the topological charge of the LG-cavity mode, and the temperature of the environment on the steady-state optomechanical entanglement. We find that cross-Kerr nonlinearity can significantly enhance steady-state optomechanical entanglement and make steady-state optomechanical entanglement more robust against the temperature of the thermal environment.