Distant Entanglement Generation between Magnon and Superconducting Qubits in Magnon-Mediated Hybrid Systems

TL;DR

This work addresses the challenge of generating entanglement across distant quantum nodes by leveraging magnon-mediated hybrid systems. It introduces a two-stage protocol: first, deterministic Bell-state generation between a local superconducting qubit (SQ) and a local magnonic system (QM1) using invariant-based shortcuts to adiabaticity (STA); second, coherent transfer of this entanglement to a remote magnonic node (QM2) via an engineered effective magnon Hamiltonian, $H_{ ext{Remote}}^{ ext{eff}} = g_{ ext{eff}} m_R^\dagger m_L + g_{ ext{eff}}^* m_L^\dagger m_R$ with $g_{ ext{eff}}=rac{2i}{g} G_L G_R$. Numerical simulations under realistic decoherence yield fidelity $F > 0.90$ and negativity $ abla_2 > 0.40$, demonstrating robust distant entanglement and highlighting the scheme's viability for scalable quantum networks. By treating magnons as both qubits and mediators, the approach reduces hardware complexity and enhances integrability, with clear pathways to multi-node extensions as coupling strengths improve. Overall, the protocol provides a practical, high-fidelity route to long-distance quantum communication in magnon-based hybrid architectures.

Abstract

We propose an efficient two-stage protocol for generating distant entanglement in a magnon-mediated hybrid quantum system, where magnons serve dual roles as both interaction mediators and qubits. This integrated design reduces the physical component count while leveraging the inherent advantages of magnons, such as their strong coupling via magnetic dipole interactions, low dissipation, and high integrability. In our setup, a superconducting resonator interfaces between a local superconducting qubit (SQ) and a local magnonic system (QM1), which is waveguide-coupled to a remote magnonic system (QM2). The protocol comprises two stages: (i) deterministic Bell-state generation between the SQ and QM1 using shortcuts to adiabaticity, and (ii) coherent state transfer to QM2 via engineered Hamiltonian dynamics. This adiabatic characteristic enhances robustness against environmental dissipation. Numerical simulations under realistic noise conditions confirm strong resilience to decoherence, achieving fidelity $F > 0.90$ and negativity $\mathcal{N}_2 > 0.40$. These results establish the protocol as a scalable and practical building block for distributed quantum networks.

Figures (8)

• Figure 1: Schematic diagram of a five-part hybrid quantum system based on magnons.
• Figure 2: Coupling schematic of a five-part hybrid quantum system based on magnons. The SC mode ($c$) and WG mode ($d_{a(b)}(\omega)$ originate from quantized electromagnetic fields in the microwave cavity and waveguide, respectively. The magnon modes ($m_{L}$ and $m_{R}$) are spin-wave excitations in YIG spheres, and their frequencies can be tunable through the external field $B_0$. The whispering gallery modes (WGMs) in each YIG sphere comprise low-energy photon modes ($a_{L}$ and $a_{R}$) and high-energy photon modes ($b_{L}$ and $b_{R}$), arising from the confined photonic states owing to the material's high refractive index and spherical geometry.
• Figure 3: (a)The interactions of the SC with the SQ and QM1, the state couplings $\ket{\tilde{g}1}_{qc} \leftrightarrow \ket{\tilde{e}0}_{qc}$ and $\ket{10}_{cm_{L}} \leftrightarrow \ket{01}_{cm_{L}}$. (b)Within the logical state basis: $\ket{\tilde{e}00\tilde{0}}$, $\ket{\tilde{g}10\tilde{0}}$, and $\ket{\tilde{g}01\tilde{0}}$, the coupling between $\ket{\tilde{e}00\tilde{0}}$ and $\ket{\tilde{g}01\tilde{0}}$ through the intermediate state $\ket{\tilde{g}10\tilde{0}}$.
• Figure 4: (a)The simplified coupling diagram. (b)We use five logical states to describe the coupling between the four subsystems, where $g_{\mathrm{eff}}$ represents the effective coupling strength between $m_{L}$ and $m_{R}$. $\ket{\tilde{g}00\tilde{0}}_{qcm_{L}m_{R}}$ represents the state in which all subsystems are in their ground states.
• Figure 5: Designed temporal profiles of the effective coupling strengths $G_{{L}/{R}}(t)$ and $g_{\mathrm{eff}}(t)$.