Abstract In this study, a scheme is proposed to generate nonreciprocal strong mechanical squeezing in a cavity‐magnon optomechanical system based on the Kerr nonlinearity of the yttrium‐iron garnet (YIG) sphere. It is found that the magnon squeezing can be directly produced by the Kerr effect and it can induce strong mechanical squeezing through the squeezing transfer achieved by the cavity‐magnon interaction and the optomechanical interaction. The results further show that the mechanical mode coupled to the cavity can achieve squeezing effect in the selected magnetic field direction, but not in the opposite one. Moreover, by properly adjusting the magnon effective detuning and the Kerr effect strength, the degree of squeezing of the mechanical mode can even beyond the 3‐dB limit, and the optimal conditions for generating stronger squeezing are obtained. This work has important applications in the nonreciprocal quantum devices, quantum information processing, and quantum precision measurement.
Abstract In this study, a scheme is proposed to generate nonreciprocal strong mechanical squeezing in a cavity‐magnon optomechanical system based on the Kerr nonlinearity of the yttrium‐iron garnet (YIG) sphere. It is found that the magnon squeezing can be directly produced by the Kerr effect and it can induce strong mechanical squeezing through the squeezing transfer achieved by the cavity‐magnon interaction and the optomechanical interaction. The results further show that the mechanical mode coupled to the cavity can achieve squeezing effect in the selected magnetic field direction, but not in the opposite one. Moreover, by properly adjusting the magnon effective detuning and the Kerr effect strength, the degree of squeezing of the mechanical mode can even beyond the 3‐dB limit, and the optimal conditions for generating stronger squeezing are obtained. This work has important applications in the nonreciprocal quantum devices, quantum information processing, and quantum precision measurement.
We propose a scheme to achieve nonreciprocal mechanical squeezing in a hybrid Kerr-modified cavity magnomechanical system, where the magnon mode is driven by two-tone microwave fields. The nonreciprocity originates from the magnon Kerr effect. Strong mechanical squeezing beyond the 3 dB limit can be nonreciprocally generated by adjusting the magnon frequency detuning, effective magnomechanical coupling strength, as well as the damping of the oscillator and the dissipation of the cavity. Importantly, the proposed scheme is robust against environmental thermal noise and system dissipation, ensuring its feasibility under current experimental conditions. This work may pave the way for the development of nonreciprocal quantum devices, such as isolators and circulators. Furthermore, the ability to achieve such robust mechanical squeezing has significant implications for advancing quantum precision measurements in metrology and sensing, offering new opportunities for exploring quantum-enhanced technologies.
Abstract Nonreciprocal devices, allowing to manipulate one‐way signals, are crucial to quantum information processing and quantum networks. Here a nonlinear cavity‐magnon system is proposed, consisting of a microwave cavity coupled to one or two yttrium–iron–garnet (YIG) spheres supporting magnons with Kerr nonlinearity, to investigate nonreciprocal unconventional photon blockade. The nonreciprocity originates from the direction‐dependent Kerr effect, distinctly different from previous proposals with spinning cavities and dissipative couplings. For a single sphere case, nonreciprocal unconventional photon blockade can be realized by manipulating the nonreciprocal destructive interference between two active paths, via varying the Kerr coefficient from positive to negative, or vice versa. By optimizing the system parameters, the perfect and well‐tuned nonreciprocal unconventional photon blockade can be predicted. For the case of two spheres with opposite Kerr effects, only reciprocal unconventional photon blockade can be observed when two cavity‐magnon coupling strengths Kerr strengths are symmetric. However, when coupling strengths or Kerr strengths become asymmetric, nonreciprocal unconventional photon blockade appears. This implies that two‐sphere nonlinear cavity‐magnon systems can be used to switch the transition between reciprocal and nonreciprocal unconventional photon blockades. This study offers a potential platform for investigating the nonreciprocal photon blockade effect in nonlinear cavity magnonics.
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 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.
We theoretically propose a scheme for generating nonreciprocal macroscopic bipartite and tripartite entanglement using the Barnett effect in cavity-magnon optomechanics. The system consists of an optomechanical cavity and a rotatable yttrium iron garnet (YIG) sphere. Our results indicate that under appropriate parameter conditions, both bipartite entanglement and genuine tripartite entanglement can be generated between the cavity mode, mechanical mode, and magnon mode. Moreover, when the YIG sphere rotates, adjusting the magnetic field direction can induce a positive or negative Barnett shift, which leads to the nonreciprocity of entanglement, where entanglement exists in one chosen magnetic field direction and disappears in the other. Meanwhile, the macroscopic tripartite entanglement in the system is robust against thermal noise. Our work provides a possible avenue for quantum information processing, quantum chiral device integration, and multi-node quantum networks construction.
ABSTRACT We study a dissipative opto‐magnomechanical system implemented using a yttrium iron garnet (YIG) sphere, which supports a magnon mode and two optical whispering‐gallery modes coupled via magnon‐induced Brillouin scattering. Besides, another mechanical mode is considered, which interacts with the optical and magnon modes through radiation pressure and magnetostriction, respectively. This hybrid system is under combined optical driving for the optical modes and microwave driving for the magnon mode and the amplitude of the microwave field is periodically modulated. We apply different parametric approximations by strongly driving one of the optical modes for preparing squeezing and entangled states, respectively. When the classical driving fields are red‐detuned, strong mechanical squeezing beyond the 3‐dB limit is achieved, along with simultaneous squeezing of all three modes. In addition, when the microwave field is red‐detuned and the optical laser is blue‐detuned, significant bipartite and tripartite entanglement is generated. These quantum entanglements are markedly enhanced by periodic modulation compared to the non‐modulated case. The proposed configurations exhibit strong robustness against system dissipation and environmental temperature, suggesting their potential as quantum resources for metrology and information processing applications.