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Physical Review Research

Stable spin squeezing of nitrogen-vacancy centers via Floquet-driven magnons

Anying Feng, Ziyu Zhou, Jun Xu, Xiangming Hu

Published Jan 26, 2026• 0 citations
Publisher

Abstract

We propose an efficient scheme for generating a stable spin-squeezed state in a hybrid magnon-nitrogen-vacancy (NV) centers system via magnon-Floquet driving. The system consists of a yttrium iron garnet (YIG) film directly coupled to NV centers that are equidistant from the film surface, and at the same time the YIG film is driven by a Floquet field. The magnon dissipation is exploited to distribute the NV centers into the dark state, manifesting as the stable spin-squeezed state. We show that the system exhibits the low- or high-energy dark state, which is determined by whether the lowering or the raising spin operator plays the dominant role in evolution. Furthermore, we also show that the spin squeezing is robust against thermal effects and decoherence, and it is possible to detect the change in N at the single-spin level, since it exhibits a distinct odd-even effect. This scheme provides a feasible way for experimental implementation and thus has potential applications in quantum information processing, quantum simulation, and precision metrology.

DOI
10.1103/hkc6-jxrs

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We propose an efficient scheme for generating a stable spin-squeezed state in a hybrid magnon-nitrogen-vacancy (NV) centers system via magnon-Floquet driving. The system consists of a yttrium iron garnet (YIG) film directly coupled to NV centers that are equidistant from the film surface, and at the same time the YIG film is driven by a Floquet field. The magnon dissipation is exploited to distribute the NV centers into the dark state, manifesting as the stable spin-squeezed state. We show that the system exhibits the low- or high-energy dark state, which is determined by whether the lowering or the raising spin operator plays the dominant role in evolution. Furthermore, we also show that the spin squeezing is robust against thermal effects and decoherence, and it is possible to detect the change in N at the single-spin level, since it exhibits a distinct odd-even effect. This scheme provides a feasible way for experimental implementation and thus has potential applications in quantum information processing, quantum simulation, and precision metrology.
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.
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.
Squeezed states, crucial for quantum metrology and emerging quantum technologies, have been demonstrated in various platforms, but quantum squeezing of magnons in macroscopic spin systems remains elusive. Here we report the experimental observation of quantum-level magnon squeezing in a millimeter-scale yttrium iron garnet (YIG) sphere. By engineering a strong dispersive magnon-superconducting qubit coupling via a microwave cavity, we implement a significant self-Kerr nonlinearity to generate squeezed magnon states with their mean magnon number less than one. Harnessing a magnon-assisted Raman process, we perform Wigner tomography, revealing quadrature variances of ∼ ⁣0.8\sim\!0.8∼0.8 (∼ ⁣1.0\sim\!1.0∼1.0~dB squeezing) relative to the vacuum. These results lay the groundwork for quantum nonlinear magnonics and promise potential applications in quantum metrology.
We propose a quantum memory scheme to transfer and store the quantum state of a superconducting flux qubit (FQ) into the electron spin of a single nitrogen-vacancy (NV) center in diamond via yttrium iron garnet (YIG), a ferromagnet. Unlike an ensemble of NV centers, the YIG moderator can enhance the effective FQ-NV-center coupling strength without introducing additional appreciable decoherence. We derive the effective interaction between the FQ and the NV center by tracing out the degrees of freedom of the collective mode of the YIG spins. We demonstrate the transfer, storage, and retrieval procedures, taking into account the effects of spontaneous decay and pure dephasing. Using realistic experimental parameters for the FQ, NV center and YIG, we find that a combined transfer, storage, and retrieval fidelity higher than 0.9, with a long storage time of 10 ms, can be achieved. This hybrid system not only acts as a promising quantum memory, but also provides an example of enhanced coupling between various systems through collective degrees of freedom.
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 spin in diamond and a 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 sequeezed magnons is exponentially enhanced}, which produces two cavity-magnon polaritons, i.e., the high-frequency polariton (HP) and 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 polarition is a potential interface to realize strong spin-spin coupling and manipulates remote solid spins.
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.