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Photonics

Nonreciprocal Genuine Microwave Entanglement via Magnon Kerr Nonlinearity

Zongchi Lv, Guangling Cheng, Jiansong Zhang, Aixi Chen

Published Dec 26, 2025• 1 citation
Publisher

Abstract

We present a utilization of the magnon Kerr effect to generate nonreciprocal genuine microwave entanglement in a hybrid system consisting of a yttrium iron garnet (YIG) sphere and three microwave cavities. Based on the quantum Langevin theory and linearization method under the condition of strong magnon driving, the system dynamics and covariance evolution are deduced and then applied to determinate the quantum correlations. It is found that three microwave cavities entangle with each other at the steady state. The basic root is that the Kerr nonlinearity can not only induce the enhanced parametric amplification of magnon but also cause the magnon frequency shift. Naturally, when the direction of the externally applied bias magnetic field is changed, switching of the magnon Kerr coefficient from positive to negative occurs and nonreciprocal tripartite entanglement among three microwave photons can be achieved. This may provide a fundamental resource for practical applications in quantum information processing and quantum networks.

DOI
10.3390/photonics13010023

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We present a utilization of the magnon Kerr effect to generate nonreciprocal genuine microwave entanglement in a hybrid system consisting of a yttrium iron garnet (YIG) sphere and three microwave cavities. Based on the quantum Langevin theory and linearization method under the condition of strong magnon driving, the system dynamics and covariance evolution are deduced and then applied to determinate the quantum correlations. It is found that three microwave cavities entangle with each other at the steady state. The basic root is that the Kerr nonlinearity can not only induce the enhanced parametric amplification of magnon but also cause the magnon frequency shift. Naturally, when the direction of the externally applied bias magnetic field is changed, switching of the magnon Kerr coefficient from positive to negative occurs and nonreciprocal tripartite entanglement among three microwave photons can be achieved. This may provide a fundamental resource for practical applications in quantum information processing and quantum networks.
We demonstrate nonreciprocal macroscopic entanglement between magnon modes in two yttrium-iron-garnet (YIG) spheres induced by the Kerr effect stemming from magnetocrystalline anisotropy. The two YIG spheres with different sizes are placed in a microwave cavity, and the magnon modes couple to the microwave cavity photons by the magnetic dipole interaction. The microwave cavity can be adiabatically eliminated by far detuning from the magnon modes, and thus mediates the indirect interaction between two magnon modes. The magnon Kerr nonlinearity of the small YIG sphere is enhanced by the appropriate drive. Meanwhile, the sign of the Kerr coefficient can be manipulated by changing the direction of the bias magnetic field, in turn causing the nonreciprocity of magnon-magnon entanglement. We numerically analyze the optimal parameter regions for generating the entanglement. The properties of the nonreciprocal entanglement are explored by analyzing the defined bidirectional contrast ratio, which reveals the different strategies for controlling the nonreciprocity of the entanglement. The presented scheme provides an alternative method for the nonreciprocal macroscopic entanglement and may have potential applications in nonreciprocal quantum devices and macroscopic quantum effects.
Abstract We propose to utilize magnon Kerr nonlinearity to generate and control microwave–microwave Einstein–Podolsky–Rosen (EPR) steering in a cavity magnonic system consisting of two microwave cavities and an yttrium iron garnet (YIG) sphere, where the magnon mode in the YIG sphere is driven by an electromagnetic field. The results show that Kerr nonlinearity of the magnon could not only sensibly induce enhanced entanglement of two microwave fields but also produce asymmetric EPR steering with different ratios of two damping rates and coupling constants. Moreover, it is found that the nonreciprocity of the steady-state EPR steering is obtainable by controlling the sign of the magnon Kerr parameter, which could be tuned from positive to negative by changing the direction of the static magnetic field. The demonstrated nonreciprocal EPR steering is of fundamental interest for the manipulation of quantum states, and may provide potential applications in quantum information tasks.
We propose a scheme to generate nonreciprocal entanglement between an yttrium iron garnet (YIG) sphere and two nitrogen-vacancy-center ensembles by magnon Kerr effects in a transmission-line resonator. By driving the YIG sphere appropriately, strong Kerr nonlinearities emerge and then induce magnon parametric amplification and magnon frequency shift, resulting in the appearance of optimal entanglements. Depending on the direction of the bias magnetic field, macroscopic nonreciprocal entanglement is realized in this all-solid-state quantum system, which may find potential applications in chiral quantum information processing.
We propose a scheme for realizing nonreciprocal bipartite and tripartite entanglement in a hybrid cavity optomagnonic system. The system consists of a tunable Fabry-Perot (FP) cavity and a microwave cavity, an yttrium iron garnet slab (YIG1) and a rotating yttrium iron garnet sphere (YIG2). The magnon modes in both YIG1 and YIG2 are strongly coupled to the microwave cavity mode, and the magnon mode in YIG1 also has a three-mode resonant interaction with the optical modes in the FP cavity. The Barnett effect causes a frequency shift of the magnon mode in YIG2. By reversing the external bias magnetic field of YIG2 to control the sign of the Barnett frequency shift, one can not only switch the entanglement partner of the optical mode between the magnon and microwave modes, but also achieve perfect on-off control of bipartite optical-microwave entanglement and tripartite optical-magnon-microwave entanglement. The study presents a flexible control scheme to realize nonreciprocal bipartite and tripartite entanglement in quantum nodes that integrate diverse physical systems such as optics, magnons, and microwaves, and may have potential applications in entanglement-based quantum networks.
We present an alternative scheme to achieve nonreciprocal unconventional magnon blockade (NUMB) in a hybrid system formed by two microwave cavities and one yttrium iron garnet (YIG) sphere, where the pump and signal cavities interact nonlinearly with each other and the signal cavity is coupled to the YIG sphere. It is found that the nonlinear coupling occurs between the pump cavity and magnon modes due to the dispersive interactions among three bosonic modes. Meanwhile, the Kerr nonlinearity is present in the pump cavity. Based on these nonlinear effects, a nonreciprocal magnon blockade could be achieved with the help of weak parametric driving of the pump cavity. The present work provides an alternative method to prepare single magnon resource, which may be helpful for quantum information processing.
We propose a theoretical scheme for the generation of nonreciprocal multipartite entanglement in a two-mode cavity magnomechanical system, consisting of two cross-microwave (MW) cavities having a yttrium iron garnet (YIG) sphere, which is coupled through magnetic dipole interaction. Our results show that the self-Kerr effect of magnon can significantly enhance multipartite entanglement, which turns out to be nonreciprocal when the magnetic field is tuned along the crystallographic axis [110]. This is due to the frequency shift on the magnons (YIG sphere), which depends on the direction of the magnetic field. Interestingly, the degree of nonreciprocity of bipartite entanglements depends upon a careful optimal choice of system parameters like normalized cavity detunings, bipartite nonlinear index, self-Kerr coefficient, and effective magnomechanical coupling rate G. In addition to bipartite entanglement, we also present the idea of a bidirectional contrast ratio, which quantifies the nonreciprocity in tripartite entanglements. Our present theoretical proposal for nonreciprocity in multipartite entanglement may find applications in diverse engineering nonreciprocal devices