We theoretically propose a scheme to realize quantum entanglement between two center-of-mass motion (CM) as the external degrees of freedom of two separated levitated yttrium iron garnet spheres. The microwave cavity field is introduced to bridge the interaction between the two separated micromagnet spheres. The optimal condition for getting entanglement between the two CM modes with and without effective cavity-magnon interaction cases are investigated. It is found that the entanglement between two CM modes could be obtained by choosing the appropriate magnon detunings for each case. The effect of the coupling strength and the thermal occupation on the entanglement are also discussed. To realize the entanglement between to CM modes, it is necessary to balance the related parametric interaction and beam splitter interaction. The results show that the CM-CM entanglement is robust against the thermal noise. This scheme would be valuable for quantum network generation and quantum information processing.
We theoretically propose a scheme to realize quantum entanglement between two center-of-mass motion (CM) as the external degrees of freedom of two separated levitated yttrium iron garnet spheres. The microwave cavity field is introduced to bridge the interaction between the two separated micromagnet spheres. The optimal condition for getting entanglement between the two CM modes with and without effective cavity-magnon interaction cases are investigated. It is found that the entanglement between two CM modes could be obtained by choosing the appropriate magnon detunings for each case. The effect of the coupling strength and the thermal occupation on the entanglement are also discussed. To realize the entanglement between to CM modes, it is necessary to balance the related parametric interaction and beam splitter interaction. The results show that the CM-CM entanglement is robust against the thermal noise. This scheme would be valuable for quantum network generation and quantum information processing.
Entanglement formation between the magnons as the internal degrees of freedom and the center-of-mass motion (CM) as the external degrees of freedom of a levitated yttrium iron garnet (YIG) sphere in a cavity-magnomechanical system is studied. Here, we propose a scheme for generating magnon-CM entanglement independent from the mass and size of the sphere in the hybrid magnonic system by driving the magnon with the parametric amplification. First, we show that the power and frequency of the driving field significantly affect this entanglement, since the driving field increases effective magnon-CM coupling. But, by increasing the magnon damping rate, this entanglement considerably decreases. Moreover, in the next step, we demonstrate the manipulation and enhancement of this entanglement by driving the magnon into the squeezed state. Our results present an approach for preparing quantum states and may find promising applications in the quantum metrology and sensing.
Abstract This work looks at the quantum entanglement between the cavity microwave and center-of-mass motion of a ferrimagnetic yttrium-iron-garnet (YIG) sphere levitated in two microwave cavities. In such a cavity magnomechanical (CMM) system, the magnons, i.e. quanta of collective spin-wave excitations in the YIG sphere, are coupled to a center-of-mass displacement via intense CMM coupling in a strongly driven cavity, and are simultaneously coupled to the other cavity via magnetic dipole interaction. We reveal that the detuning condition is necessary to improve the mediation effect of the magnon for generating macroscopic entanglement. In particular, this center-of-mass motion can be adjusted by suitable levitation technology, unlike the mechanical deformation limited by the fixed structure of the YIG sphere in a standard CMM system. We also indicate that the entanglement via the unique CMM coupling is independent of the size and mass of the YIG sphere, and it is beneficial to explore the macroscopic entanglement effect in combination with size-independent cooling. These findings suggest that our scheme may open up an alternative and novel direction in the exploration and application of macroscopic quantum effects.
Generating multipartite entanglement is always a popular research field in quantum information processing and quantum optics. In this paper, we propose a scheme to realize all bipartite entanglements and the genuine tripartite entanglement among photon, magnon, and phonon modes in a cavity-magnomechanical system. The center-of-mass motion of a yttrium iron garnet sphere couples to the magnon and constitutes photon-magnon-phonon tripartite interaction. By modulating the detuning between the cavity (magnon) mode and the driven field, we can obtain the optimal photon-phonon entanglement or magnon-phonon entanglement. The genuine tripartite entanglement can be prepared through a suitable detuning. We compare the different entanglement cases with and without effective direct cavity-magnon coupling. The results indicate that the photon-magnon entanglement can be enhanced by the effective cavity-magnon coupling strength, and all bipartite entanglements show greater robustness against the thermal phonon number. This investigation should be useful for phonon-involved multipartite quantum information processing and quantum precision measurement.
We theoretically propose a cavity magnomechanical system with a levitated yttrium iron garnet sphere to study the entanglement characteristics between subsystems. The system consists of microwave photon, magnon, and mechanical phonon modes, where the photon and magnon modes can be driven by external microwave sources. We find that with the appropriate choice of the suspension position, the effective couplings between the cavity field and the magnon and phonon modes can be established, thus inducing the generation of bipartite entanglement and genuine tripartite entanglement in the system. Further, we also analyze in detail the influences of the radius of the sphere, the detunings of the cavity and magnon modes, the driving power, the frequency of the phonon mode, and the environment temperature on the characteristics of the quantum entanglement. The results obtained here indicate that the bipartite and tripartite entanglements can be manipulated by changing the radius and the oscillation frequency of the sphere in addition to changing the parameters of the cavity field, and therefore, the levitated magnomechanical system has a potential application in the study of macroscopic quantum phenomena.
We propose a scheme to generate entanglement between magnon and superconducting qubit. The macroscopic yttrium–iron–garnet sphere and superconducting qubit are installed in two spatially separated cavities, which are directly driven by a two-mode squeezed-vacuum microwave field. The magnon and cavity 1 are coupled via magnetic dipole interaction and the superconducting qubit and cavity 2 are coupled via electric dipole interaction. We theoretically demonstrate that the magnon–qubit steady-state entanglement can be created by transferring quantum correlations of the two-mode squeezed-vacuum driving field via cavity–magnon and cavity–qubit beam-splitter interactions. The transfer is highly efficient, and the entanglement is robust against temperature in the optimal parameter regimes. We also deduce a new, to the best of our knowledge, mathematical method to analyze the dynamics of the magnon–qubit entanglement and some significant results are obtained. Our scheme can be implemented with experimentally feasible parameters and may provide guidance in designing hybrid quantum networks.
We propose a scheme to realize robust optical entanglement in cavity optomagnonics, where two optical whispering gallery modes (WGMs) couple to a magnon mode in a yttrium iron garnet (YIG) sphere. The beam-splitter-like and two-mode squeezing magnon-photon interactions can be realized simultaneously when the two optical WGMs are driven by external fields. Entanglement between the two optical modes is then generated via their coupling with magnons. By exploiting the destructive quantum interference between the bright modes of the interface, the effects of initial thermal occupations of magnons can be eliminated. Moreover, the excitation of the Bogoliubov dark mode is capable of protecting the optical entanglement from thermal heating effects. Therefore, the generated optical entanglement is robust against thermal noise and the requirement of cooling the magnon mode is relaxed. Our scheme may find applications in the study of magnon-based quantum information processing.