Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2607.25643

Nonlocal Magnonic Cat States in Hybrid Magnon-Qubit Architectures

Urmimala Dewan, Roson Nongthombam, Sampreet Kalita, Amarendra K. Sarma

quant-phSubmitted Jul 28, 2026• Announced Jul 29, 2026• 0 citations
arXivHTMLPDF

Abstract

The quantum superpositions of coherent states offer an alternative to the conventional qubit-based encodings by harnessing the large Hilbert space available in bosonic modes, including those realised in microwave and optical cavities, magnons, and mechanical resonators. Beyond their advantages for local information processing, establishing long-distance quantum networks for such bosonic states is crucial for scalable quantum communication and distributed quantum computation. In this work, we propose an entanglement-swapping-based protocol to generate a bipartite magnonic cat state shared between spatially separated subsystems. Each subsystem comprises a hybrid architecture consisting of a superconducting transmon qubit coupled to a yttrium iron garnet (YIG) sphere that supports magnon modes. By performing a projective Bell-state measurement on the qubits, the initially established magnon-qubit entanglement is coherently transferred to the remote magnon modes, resulting in a nonlocal magnonic cat state. For experimental characterisation of the gener- ated states, we perform quantum state tomography through reconstruction of the Wigner function using joint displaced parity measurements of the magnon modes. Our scheme provides a feasible route towards realising long-distance magnonic entanglement and contributes to the advancement of hybrid quantum network architectures.

Related papers

Preparing two-mode magnonic Schrödinger cat states in a cavity-magnon-qubit system

Gen Li, Gang Liu, Rong-Can Yang +1 more

The cavity-magnon-qubit system has recently been demonstrated as a new platform for preparing macroscopic quantum states in magnonic systems. Here, we propose to prepare a two-mode magnonic cat state, which is also a non-Gaussian entangled state, based on this practical system involving two yttrium-iron-garnet (YIG) spheres and a superconducting qubit coupled to a common microwave cavity. By adiabatically eliminating the cavity and resonantly driving the qubit, an effective magnon-qubit conditional-displacement interaction is achieved. Further working in the magnon-magnon strong-coupling regime and considering two identical magnon frequencies and coupling strengths to the cavity, two hybridized magnon modes are formed, of which the bright mode is prepared in a cat state after a projective measurement on the qubit, while the dark mode remains in its initial vacuum state. Such a state corresponds to a two-mode cat state of two original magnon modes, which share strong non-Gaussian entanglement. We also discuss practical dissipation and dephasing effects on the cat state. The results indicate that strong nonclassicality and non-Gaussian entanglement are present in the two-mode cat state using fully feasible parameters.

quant-pharXiv:2606.25511•Jun 25, 2026•0 citations

Quantum entanglement generation on magnons assisted with microwave cavities coupled to a superconducting qubit

Jiuming Li, Shao-Ming Fei

We present protocols to generate quantum entanglement on nonlocal magnons in hybrid systems composed of yttrium iron garnet (YIG) spheres, microwave cavities and a superconducting (SC) qubit. In the schemes, the YIGs are coupled to respective microwave cavities in resonant way, and the SC qubit is placed at the center of the cavities, which interacts with the cavities simultaneously. By exchanging the virtual photon, the cavities can indirectly interact in the far-detuning regime. Detailed protocols are presented to establish entanglement for two, three and arbitrary N magnons with reasonable fidelities.

arXiv:2301.05820•Frontiers of Physics•Feb 13, 2023•10 citations

Generation of magnonic squeezed state and its superposition in a hybrid qubit-magnon system

Gang Liu, Junpeng Liu, Feng Qiao +1 more

We propose a protocol for generating magnonic squeezed states (MSS) and their superpositions (SMSS) in a hybrid system comprising a superconducting flux qubit magnetically coupled to the Kittel mode of a yttrium iron garnet (YIG) sphere. The flux qubit provides an intrinsic longitudinal interaction with the magnon mode, which, under resonant microwave driving, gives rise to an effective qubit-state-dependent squeezing Hamiltonian. Numerical simulations incorporating realistic dissipation demonstrate that magnon quadrature noise reduction exceeding $8~\mathrm{dB}$ is achievable with experimentally accessible parameters.~By preparing the qubit in a superposition state followed by projective measurement, we further obtain symmetric and antisymmetric superpositions of orthogonally squeezed magnon states exhibiting clear phase-space interference fringes.~We discuss how the fourfold rotational symmetry of these states supports a bosonic logical encoding with potential for protecting against dominant error channels in magnonic platforms.

quant-pharXiv:2604.02924•Apr 6, 2026•0 citations

Quantum magnon conversion accompanying magnon antibunching

Yaqi Fan, Jiahua Li, Ying Wu

The implementation of quantum network made up of multiple nodes and channels needs to take advantage of hybrid quantum systems. So far, in the hybrid ferromagnet-superconductor quantum system, the establishment of the remote effective interactions based on the virtual photons exchange mediated by the microwave cavity mode has been experimentally confirmed, providing a physical basis for the implementation of the remote signal transfer from one node to another. In this work, we put forward a magnon-based hybrid quantum system consisting of two macroscopic spin subsystems [i.e., millimeter-diameter ferromagnetic yttrium-iron-garnet (YIG) spheres] and one transmon-type superconducting qubit, and show that the mechanism of the cavity-mediated remote magnon-mode intertalk is feasible for achieving microwave signal transfer, simultaneously accompanied by a transition from Poissonian to sub-Poissonian statistics. We find that by tuning the typical system parameters properly, even if there is a mismatch in magnon-mode frequencies or dissipation rates between the two YIG spheres, the microwave information transfer from one YIG sphere to another is still robust, where the signal output through another YIG sphere exhibits pronounced antibunching. In addition, the proposed hybrid quantum system possesses a robustness window against the dissipation rates of both the qubit and the two Kittel modes. The analytical calculations and numerical simulations are conducted under experimentally accessible conditions, and the consistency of the results attained by these two methods makes our research more credible. Physically, we notice that two conversion channels are opened. One channel comes from the linear coupling. The other is based on the nonlinear interaction, which also is the underlying mechanism responsible for nonclassical sub-Poissonian signal output.

Physical Review A•Aug 23, 2024•4 citations

Long-range generation of a magnon-magnon entangled state

Ya-long Ren, Ji-kun Xie, Xinke Li +2 more

Generation of entanglement between spatially separated macroscopic systems enables quantum networks and fundamental tests of quantum theory. Here, we propose a scheme to generate a long-range entangled state between two macroscopic spheres. The hybrid system under consideration consists of two massive ferromagnetic spheres and a superconducting transmon qubit, which are both coupled to a microwave cavity array. When the qubit or magnon frequency lies outside of the frequency band of the cavity array, the qubit or magnon mode can seed a tunable, localized cavity mode with an exponentially decaying envelope around its position. This effective cavity mediates the long-range qubit-magnon and magnon-magnon interactions in a coherent way, enabling the long-distance magnon-magnon entanglement via the superconducting qubit.

Physical review. B./Physical review. B•Mar 16, 2022•64 citations

Steady-state entanglement of spin qubits mediated by nonreciprocal and chiral magnons

Martijn Dols, Mikhail A. Cherkasskii, Victor A. S. V. Bittencourt +3 more

We propose a hybrid quantum system in which a magnet supporting nonreciprocal magnons, chiral magnons, or both mediates the dissipative and unidirectional coupling of spin qubits. By driving the qubits, the steady state of this qubit-qubit coupling scheme becomes the maximally entangled Bell state. We devise a protocol where the system converges to this entangled state and benchmark it including qubit decay and dephasing. The protocol is numerically tested on a hybrid system consisting of nitrogen-vacancy (NV) centers coupled to magnon surface modes of a yttrium iron garnet (YIG) film. We show that the dephasing time of the NV centers forms the bottleneck for achieving the entanglement of NV centers separated by a distance within the magnon coherence length. Our findings identify the key technological requirements and demonstrate a viable route toward steady-state entanglement of solid-state spins over distances of several microns using magnonic quantum networks, expanding the toolbox of magnonics for quantum information purposes.

arXiv:2509.13094•Physical Review Research•May 21, 2026•1 citation
The quantum superpositions of coherent states offer an alternative to the conventional qubit-based encodings by harnessing the large Hilbert space available in bosonic modes, including those realised in microwave and optical cavities, magnons, and mechanical resonators. Beyond their advantages for local information processing, establishing long-distance quantum networks for such bosonic states is crucial for scalable quantum communication and distributed quantum computation. In this work, we propose an entanglement-swapping-based protocol to generate a bipartite magnonic cat state shared between spatially separated subsystems. Each subsystem comprises a hybrid architecture consisting of a superconducting transmon qubit coupled to a yttrium iron garnet (YIG) sphere that supports magnon modes. By performing a projective Bell-state measurement on the qubits, the initially established magnon-qubit entanglement is coherently transferred to the remote magnon modes, resulting in a nonlocal magnonic cat state. For experimental characterisation of the gener- ated states, we perform quantum state tomography through reconstruction of the Wigner function using joint displaced parity measurements of the magnon modes. Our scheme provides a feasible route towards realising long-distance magnonic entanglement and contributes to the advancement of hybrid quantum network architectures.
The cavity-magnon-qubit system has recently been demonstrated as a new platform for preparing macroscopic quantum states in magnonic systems. Here, we propose to prepare a two-mode magnonic cat state, which is also a non-Gaussian entangled state, based on this practical system involving two yttrium-iron-garnet (YIG) spheres and a superconducting qubit coupled to a common microwave cavity. By adiabatically eliminating the cavity and resonantly driving the qubit, an effective magnon-qubit conditional-displacement interaction is achieved. Further working in the magnon-magnon strong-coupling regime and considering two identical magnon frequencies and coupling strengths to the cavity, two hybridized magnon modes are formed, of which the bright mode is prepared in a cat state after a projective measurement on the qubit, while the dark mode remains in its initial vacuum state. Such a state corresponds to a two-mode cat state of two original magnon modes, which share strong non-Gaussian entanglement. We also discuss practical dissipation and dephasing effects on the cat state. The results indicate that strong nonclassicality and non-Gaussian entanglement are present in the two-mode cat state using fully feasible parameters.
We present protocols to generate quantum entanglement on nonlocal magnons in hybrid systems composed of yttrium iron garnet (YIG) spheres, microwave cavities and a superconducting (SC) qubit. In the schemes, the YIGs are coupled to respective microwave cavities in resonant way, and the SC qubit is placed at the center of the cavities, which interacts with the cavities simultaneously. By exchanging the virtual photon, the cavities can indirectly interact in the far-detuning regime. Detailed protocols are presented to establish entanglement for two, three and arbitrary N magnons with reasonable fidelities.
We propose a protocol for generating magnonic squeezed states (MSS) and their superpositions (SMSS) in a hybrid system comprising a superconducting flux qubit magnetically coupled to the Kittel mode of a yttrium iron garnet (YIG) sphere. The flux qubit provides an intrinsic longitudinal interaction with the magnon mode, which, under resonant microwave driving, gives rise to an effective qubit-state-dependent squeezing Hamiltonian. Numerical simulations incorporating realistic dissipation demonstrate that magnon quadrature noise reduction exceeding 8 dB8~\mathrm{dB}8 dB is achievable with experimentally accessible parameters.~By preparing the qubit in a superposition state followed by projective measurement, we further obtain symmetric and antisymmetric superpositions of orthogonally squeezed magnon states exhibiting clear phase-space interference fringes.~We discuss how the fourfold rotational symmetry of these states supports a bosonic logical encoding with potential for protecting against dominant error channels in magnonic platforms.
The implementation of quantum network made up of multiple nodes and channels needs to take advantage of hybrid quantum systems. So far, in the hybrid ferromagnet-superconductor quantum system, the establishment of the remote effective interactions based on the virtual photons exchange mediated by the microwave cavity mode has been experimentally confirmed, providing a physical basis for the implementation of the remote signal transfer from one node to another. In this work, we put forward a magnon-based hybrid quantum system consisting of two macroscopic spin subsystems [i.e., millimeter-diameter ferromagnetic yttrium-iron-garnet (YIG) spheres] and one transmon-type superconducting qubit, and show that the mechanism of the cavity-mediated remote magnon-mode intertalk is feasible for achieving microwave signal transfer, simultaneously accompanied by a transition from Poissonian to sub-Poissonian statistics. We find that by tuning the typical system parameters properly, even if there is a mismatch in magnon-mode frequencies or dissipation rates between the two YIG spheres, the microwave information transfer from one YIG sphere to another is still robust, where the signal output through another YIG sphere exhibits pronounced antibunching. In addition, the proposed hybrid quantum system possesses a robustness window against the dissipation rates of both the qubit and the two Kittel modes. The analytical calculations and numerical simulations are conducted under experimentally accessible conditions, and the consistency of the results attained by these two methods makes our research more credible. Physically, we notice that two conversion channels are opened. One channel comes from the linear coupling. The other is based on the nonlinear interaction, which also is the underlying mechanism responsible for nonclassical sub-Poissonian signal output.
Generation of entanglement between spatially separated macroscopic systems enables quantum networks and fundamental tests of quantum theory. Here, we propose a scheme to generate a long-range entangled state between two macroscopic spheres. The hybrid system under consideration consists of two massive ferromagnetic spheres and a superconducting transmon qubit, which are both coupled to a microwave cavity array. When the qubit or magnon frequency lies outside of the frequency band of the cavity array, the qubit or magnon mode can seed a tunable, localized cavity mode with an exponentially decaying envelope around its position. This effective cavity mediates the long-range qubit-magnon and magnon-magnon interactions in a coherent way, enabling the long-distance magnon-magnon entanglement via the superconducting qubit.
We propose a hybrid quantum system in which a magnet supporting nonreciprocal magnons, chiral magnons, or both mediates the dissipative and unidirectional coupling of spin qubits. By driving the qubits, the steady state of this qubit-qubit coupling scheme becomes the maximally entangled Bell state. We devise a protocol where the system converges to this entangled state and benchmark it including qubit decay and dephasing. The protocol is numerically tested on a hybrid system consisting of nitrogen-vacancy (NV) centers coupled to magnon surface modes of a yttrium iron garnet (YIG) film. We show that the dephasing time of the NV centers forms the bottleneck for achieving the entanglement of NV centers separated by a distance within the magnon coherence length. Our findings identify the key technological requirements and demonstrate a viable route toward steady-state entanglement of solid-state spins over distances of several microns using magnonic quantum networks, expanding the toolbox of magnonics for quantum information purposes.