Magnon-Squeezing-Induced Nonreciprocal Quantum Coherence in a Cavity Magnomechanical System

TL;DR

The paper tackles nonreciprocal quantum coherence in a cavity magnomechanical system by introducing a squeezed-magnon drive and analyzing Gaussian coherence across cavity, magnon, and mechanical modes. The authors construct a detailed model with detunings $\Delta_a$, $\Delta_m$, couplings $g_{ma}$ and $g_{mb}$, drive $\Omega_l$, and a squeezing term with amplitude $ξ$ and phase $\varphi$, then linearize to obtain a Gaussian description via the Lyapunov equation $A\mathcal{V}+\mathcal{V}A^{T}+\mathcal{F}=0$ for the covariance matrix $\mathcal{V}$. They quantify single-mode and total coherence using covariance blocks, showing that the phase-dependent shifts $\Delta_\varphi=ξ\sin\varphi$ and $\gamma_\varphi=ξ\cos\varphi$ enable controlled enhancement and nonreciprocal transfer of coherence, with drive power $P_l$ and coupling $g_{ma}$ boosting coherence while thermal noise reduces it, though squeezing partially mitigates the degradation. The results establish magnon squeezing as a robust, tunable resource for controlling coherence in hybrid magnonic platforms, with implications for coherent quantum information processing and on-chip nonreciprocal devices.

Abstract

We investigate quantum coherence in a hybrid cavity magnomechanical system incorporating a squeezed-magnon drive. By analyzing the Gaussian quantum coherence of the cavity, magnonic, and mechanical subsystems, as well as the total system coherence, we identify the critical roles of phase control, coupling strength, drive power, and thermal noise. We show that the squeezing amplitude and phase precisely modulate the effective magnon frequency and damping, enabling phase-dependent enhancement and nonreciprocal transfer of coherence. Our systematic parameter analysis indicates that increasing driving power and photon-magnon coupling enhances quantum coherence, while thermal decoherence leads to its degradation. However, this effect is partially suppressed by the presence of magnon squeezing. The results show that squeezed magnons are a robust and tunable resource for controlling, stabilizing, and optimizing quantum coherence in cavity magnomechanical platforms, offering potential applications in hybrid magnonic systems and coherent quantum information processing.

Figures (6)

• Figure 1: (a) Schematic diagram of the cavity magnomechanical system consisting of a microwave cavity coupled to a YIG sphere. The YIG sphere supports both magnon ($m$) and phonon ($b$) modes. It is positioned at the magnetic field maximum of the cavity mode ($a$) while being subjected to a uniform bias magnetic field along the $z$ axis, which enables photon–magnon coupling. The magnon–phonon interaction arises from the intrinsic magnetostrictive effect. (b) Equivalent mode coupling representation of the system, where $g_{ma}$ and $g_{mb}$ denote the photon–magnon and magnon–phonon coupling strengths, respectively. The light-blue ellipse illustrates the squeezed magnon mode characterized by the squeezing parameter $\xi$ and phase $\varphi$, which can be used to enhance nonreciprocal quantum coherence.
• Figure 2: Density plots of quantum coherence: (a) $C_a$, (b) $C_m$, (c) $C_b$, and (d) $C_T$ as a function of the effective squeezing parameter $\xi$ and the phase $\varphi$. In addition, panels (a$_1$), (b$_1$), (c$_1$), and (d$_1$) show $C_a$, $C_m$, $C_b$, and $C_T$, respectively, as a function of the phase $\varphi$ for four values of the squeezing parameter: $\xi = 0$ (dashed line), $\xi = 0.5\gamma_a$ (dash–dotted line), $\xi = \gamma_a$ (dotted line), and $\xi = 1.5\gamma_a$ (solid line). The other parameters are given in the main text.
• Figure 3: Plots of quantum coherence: (a) $C_a$, (b) $C_m$, (c) $C_b$, and (d) $C_T$ as a function of the driving power $P_l$ for four values of the squeezing parameter: $\xi = 0$ (dashed line), $\xi = 0.5\gamma_a$ (dash–dotted line), $\xi = \gamma_a$ (dotted line), and $\xi = 1.5\gamma_a$ (solid line). In all cases, the optimal phase is set to $\varphi = 3\pi/2$, and the other parameters are the same as those in Fig. \ref{['F2']}.
• Figure 4: Density plots of quantum coherence: (a) $C_a$, (b) $C_m$, (c) $C_b$, and (d) $C_T$ as a function of the effective squeezing parameter $\xi$ and the coupling $g_{ma}$. In all cases, the optimal phase is set to $\varphi = 3\pi/2$, and the other parameters are the same as those in Fig. \ref{['F2']}.
• Figure 5: Plots of quantum coherence: (a) $C_a$, (b) $C_m$, (c) $C_b$, and (d) $C_T$ as a function of the environmental temperature $T$ for four values of the squeezing parameter: $\xi = 0$ (dashed line), $\xi = 0.5\gamma_a$ (dash–dotted line), $\xi = \gamma_a$ (dotted line), and $\xi = 1.5\gamma_a$ (solid line). In all cases, the optimal phase is set to $\varphi = 3\pi/2$, and the remaining parameters are the same as those in Fig. \ref{['F2']}.