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Advanced Quantum Technologies

Generation of Long‐Distance Greenberger–Horne–Zeilinger States in a Driven Hybrid Quantum System

Xin Zeng, M LI, Bo Tian, Chunfang Sun, Chunfeng Wu, Gangcheng Wang

Published Apr 1, 2026• 0 citations
Publisher

Abstract

ABSTRACT We propose a theoretical protocol for generating long‐distance Greenberger‐Horne‐Zeilinger states in a driven hybrid quantum system. The system consists of a central magnon coupled to multiple nitrogen–vacancy center spins positioned at a distance from the surface of the yttrium‐iron‐garnet sphere. A significant enhancement in the effective magnon‐spin coupling strength is achieved by driving the magnon with Kerr term. We analyze the dependence of the squeezing parameter on the driving field and adiabatically eliminate the magnonic mode under large detuning conditions via the Schrieffer–Wolff transformation, thereby establishing an effective all‐to‐all one‐axis‐twisting type spin–spin interaction essential for Greenberger–Horne–Zeilinger generation. Numerical simulations show that multi‐qubit Greenberger–Horne–Zeilinger states can be achieved even in the presence of dissipation. Furthermore, we investigate the impact of both inhomogeneous frequency broadening and non‐uniform coupling strengths between the magnon and spins. A cavity protection mechanism is introduced to mitigate frequency inhomogeneous broadening, while the tolerance to coupling inhomogeneity is also quantitatively evaluated.

DOI
10.1002/qute.70279

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ABSTRACT We propose a theoretical protocol for generating long‐distance Greenberger‐Horne‐Zeilinger states in a driven hybrid quantum system. The system consists of a central magnon coupled to multiple nitrogen–vacancy center spins positioned at a distance from the surface of the yttrium‐iron‐garnet sphere. A significant enhancement in the effective magnon‐spin coupling strength is achieved by driving the magnon with Kerr term. We analyze the dependence of the squeezing parameter on the driving field and adiabatically eliminate the magnonic mode under large detuning conditions via the Schrieffer–Wolff transformation, thereby establishing an effective all‐to‐all one‐axis‐twisting type spin–spin interaction essential for Greenberger–Horne–Zeilinger generation. Numerical simulations show that multi‐qubit Greenberger–Horne–Zeilinger states can be achieved even in the presence of dissipation. Furthermore, we investigate the impact of both inhomogeneous frequency broadening and non‐uniform coupling strengths between the magnon and spins. A cavity protection mechanism is introduced to mitigate frequency inhomogeneous broadening, while the tolerance to coupling inhomogeneity is also quantitatively evaluated.
In this study, we propose a theoretical scheme for achieving long-distance Greenberger-Horne-Zeilinger states in a driven hybrid quantum system. By applying a microwave field to the YIG sphere, we utilize the Kerr effect to induce the squeezing of the magnon, thereby achieving an exponential enhancement of the coupling strength between the magnonic mode and spins, and we also discuss in detail the relationship between the squeezing parameter and the external microwave field. By means of the Schrieffer-Wolff transformation, the magnonic mode can be adiabatically eliminated under the large detuning condition, thereby establishing a robust effective interaction between spins essential for realizing the desired entangled state. Numerical simulations indicate that the squeezing parameter can be effectively increased by adjusting the driving field, and our proposal can generate high-fidelity Greenberger-Horne-Zeilinger states even in dissipative systems. Additionally, we extensively discuss the influence of inhomogeneous broadening on the entangled states, and the experimental feasibility shows that our results provide possibilities in the realms of quantum networking and quantum computing.
Abstract Realizing strong optomechanical interaction at a few‐photon level is one of the most significant tasks in optomechanical physics. In this paper, an efficient approach to realize an enhanced optomechanical‐like coupling in a cross‐Kerr‐type coupled three‐mode optical cavity system via a driving field is presented. It is shown that the optomechanical‐like coupling can be strongly enhanced to enter the ultrastrong‐coupling regime, and the effects of cavity field damping can be effectively restrained by adjusting the driving field and the cavity frequencies. In addition, as an application of the enhanced multimode optomechanical‐like quantum system, a scheme is propsed to deterministically generate a hybrid Greenberger–Horne–Zeilinger state. Numerical simulation reveals that the scheme is reliable and robust against various dissipation effects and the fluctuations of control parameters in current technology. This work has potential applications in quantum information processing and paves the way for the study of multimode optomechanical systems.
Strong coupling between single qubits is crucial for quantum information science and quantum computation. However, it is still challenged, especially for single solid-state qubit. Here, we propose a hybrid quantum system, consisting of a coplanar waveguide (CPW) resonator weakly coupled to a single nitrogen-vacancy (NV) spin in diamond and an yttrium-iron-garnet (YIG) nanosphere holding Kerr magnons, to realize strong long-distance spin-spin coupling. With a strong driving field on magnons, the Kerr effect can squeeze magnons, and thus the coupling between the CPW resonator and the squeezed magnons is exponentially enhanced, which produces two cavity-magnon polaritons, i.e., the high-frequency polariton (HP) and the low-frequency polariton (LP). When the enhanced cavity-magnon coupling approaches the critical value (i.e., the frequency of the LP becomes zero), the spin is fully decoupled from the HP, while the coupling between the spin and the LP is significantly improved. In the dispersive regime, a strong spin-spin coupling mediated by the LP is achieved with accessible parameters. Our proposal indicates that the critical cavity-magnon polariton is a potential interface to realize strong spin-spin coupling and manipulates remote solid spins.
Strong and controllable tripartite interactions play a pivotal role in quantum information and nonlinear quantum optics, yet challenging to realize. In this work, we propose a hybrid system consisting of a nitrogen-vacancy (NV) center coupled to Kerr magnons (magnons with Kerr nonlinearity) in two yttrium-iron-garnet spheres. By adiabatically eliminating the ground state of the NV qutrit in the dispersive regime, an effective tripartite interaction among magnons and an NV qubit encoded in its excited states is obtained. In the strong driving limit, Kerr magnons can be linearized and give rise to degenerate parametric amplification for squeezing magnons. As a result, both the tripartite interaction and cooperativity are exponentially enhanced twice, which is about exp⁡(ξ)\exp(ξ)exp(ξ) times than schemes only involving single-squeezing. Hence, our proposal is more experimentally feasible because modest squeezing parameter is sufficient. With this amplified tripartite coupling strength, the system dynamics are greatly accelerated, leading to fast generation of tripartite entanglement. In addition, noise-resilient perfect magnon blockade can be achieved, well predicted by both the analytical approach and numerical simulation with quantum master equation. Our results suggest that the NV center represents a promising interface for engineering many-body interactions in quantum magnonics, offering a versatile platform for exploring fundamental quantum phenomena such as entanglement and correlations.
We propose a one-step scheme for the generation of Greenberger–Horne–Zeilinger states of multi solid-state qubits and the implementation of quantum phase gates in a system consisting of N spatially separated nitrogen-vacancy centers coupled to the whispering-gallery mode (WGM) of a microsphere cavity. The proposed scheme is based on the effective electronic dipole–dipole interaction between electron spins associated with the NV centers, which is mediated by the WGM and applying external driving laser fields. As the spontaneous emission of the excited states of the NV centers is highly suppressed and the cavity mode is only virtually excited, the scheme is insensitive to decoherence.
We propose a scheme for preparing magnon squeezed states in a hybrid cavity-magnon-qubit system. The system consists of a microwave cavity that simultaneously couples to a magnon mode of a macroscopic yttrium-iron-garnet sphere via the magnetic-dipole interaction and to a transmon-type superconducting qubit via the electric-dipole interaction. By far detuning from the magnon-qubit system, the microwave cavity is adiabatically eliminated. The magnon mode and the qubit then get effectively coupled via the mediation of virtual photons of the microwave cavity. We show that by driving the qubit with two microwave fields and by appropriately choosing the drive frequencies and strengths, magnonic parametric amplification can be realized, which leads to magnon quadrature squeezing with the noise below vacuum fluctuation. We provide optimal conditions for achieving magnon squeezing, and moderate squeezing can be obtained using currently available parameters. The generated squeezed states are of a magnon mode involving more than 1018{10}^{18}1018 spins and thus macroscopic quantum states. This work may find promising applications in quantum information processing and high-precision measurements based on magnons and in the study of macroscopic quantum states.