ABSTRACT We focus on the magnon blockade phenomenon in a non‐Hermitian cavity magnonics system with dissipative magnon–photon coupling. The system consists of a cross‐shaped microwave circuit supporting both standing and traveling waves and a yttrium iron garnet sphere supporting a magnon mode, where the dissipative coupling between the magnon mode and the standing wave cavity mode is caused by the traveling wave, forming the non‐Hermitian cavity magnonics system. For the non‐Hermitian system with the pure dissipative coupling, we find that, by driving the microwave cavity mode using the two‐photon driving field, the magnon blockade phenomenon can occur due to the destructive interference of the transition paths. More excitingly, when the non‐Hermitian cavity magnonics system is set as an anti‐parity‐time ()‐symmetry system, the optimal magnon blockade phenomenon occurs near the exceptional points (transition points from the unbroken‐ to broken‐anti‐ symmetry). Then we analyze the influence of the driving strength on the magnon blockade, and give the optimal driving strength. The presented work not only provides an alternative method for the magnon blockade, but also can promote the study of the quantum effects in the non‐Hermitian cavity magnonics system.
ABSTRACT We focus on the magnon blockade phenomenon in a non‐Hermitian cavity magnonics system with dissipative magnon–photon coupling. The system consists of a cross‐shaped microwave circuit supporting both standing and traveling waves and a yttrium iron garnet sphere supporting a magnon mode, where the dissipative coupling between the magnon mode and the standing wave cavity mode is caused by the traveling wave, forming the non‐Hermitian cavity magnonics system. For the non‐Hermitian system with the pure dissipative coupling, we find that, by driving the microwave cavity mode using the two‐photon driving field, the magnon blockade phenomenon can occur due to the destructive interference of the transition paths. More excitingly, when the non‐Hermitian cavity magnonics system is set as an anti‐parity‐time ()‐symmetry system, the optimal magnon blockade phenomenon occurs near the exceptional points (transition points from the unbroken‐ to broken‐anti‐ symmetry). Then we analyze the influence of the driving strength on the magnon blockade, and give the optimal driving strength. The presented work not only provides an alternative method for the magnon blockade, but also can promote the study of the quantum effects in the non‐Hermitian cavity magnonics system.
We present a theoretically versatile and controllable framework for realizing chirally-symmetric-like unconventional magnon blockade within a cavity-magnon system composed of a yttrium iron garnet sphere and a cross-line microwave circuit, where the cavity mode is driven by a two-photon driving field. Under optimal conditions regarding the driving strength and phase of this two-photon field, we observe that magnon blockade exhibits chiral-like symmetry even in high-dissipation scenarios. However, the introduction of coherent coupling leads to energy level splitting that counteracts the energy level attraction induced by dissipative coupling, thereby diminishing the blockade effect. Furthermore, we clarify that the energy level attraction resulting from dissipative coupling remains invariant with respect to variations in the phase of this coupling coefficient. Our approach offers promising applications for tunable single-magnon sources and quantum information processing. • A versatile and controllable framework for realizing chirally-symmetric-like unconventional magnon blockade is investigated theoretically. • Under optimal conditions regarding the driving strength and phase of this two-photon field, magnon blockade exhibits chiral-like symmetry even in high-dissipation scenarios. • The introduction of coherent coupling leads to energy level splitting that counteracts the energy level attraction induced by dissipative coupling. • The energy level attraction resulting from dissipative coupling remains invariant with respect to variations in the phase of this coupling coefficient. • There are promising applications for tunable single-magnon sources and quantum information processing.
Abstract Nonreciprocal devices, allowing to manipulate one‐way signals, are crucial to quantum information processing and quantum networks. Here a nonlinear cavity‐magnon system is proposed, consisting of a microwave cavity coupled to one or two yttrium–iron–garnet (YIG) spheres supporting magnons with Kerr nonlinearity, to investigate nonreciprocal unconventional photon blockade. The nonreciprocity originates from the direction‐dependent Kerr effect, distinctly different from previous proposals with spinning cavities and dissipative couplings. For a single sphere case, nonreciprocal unconventional photon blockade can be realized by manipulating the nonreciprocal destructive interference between two active paths, via varying the Kerr coefficient from positive to negative, or vice versa. By optimizing the system parameters, the perfect and well‐tuned nonreciprocal unconventional photon blockade can be predicted. For the case of two spheres with opposite Kerr effects, only reciprocal unconventional photon blockade can be observed when two cavity‐magnon coupling strengths Kerr strengths are symmetric. However, when coupling strengths or Kerr strengths become asymmetric, nonreciprocal unconventional photon blockade appears. This implies that two‐sphere nonlinear cavity‐magnon systems can be used to switch the transition between reciprocal and nonreciprocal unconventional photon blockades. This study offers a potential platform for investigating the nonreciprocal photon blockade effect in nonlinear cavity magnonics.
Cavity magnomechanical systems, which coherently couple magnons, photons, and phonons, offer a powerful platform for exploring quantum phenomena and developing hybrid quantum technologies. We study a non-Hermitian cavity magnomechanical system featuring a yttrium iron garnet (YIG) sphere driven by an external magnetic field, where magnons interact with cavity photons via magnetic dipole coupling and with phonons via magnetostrictive forces. Non-Hermiticity is introduced through a traveling optical field that directly excites the YIG sphere, enabling precise control over parity-time (PT) symmetry. Analysis of the eigenfrequency spectrum reveals a third-order exceptional point (EP) that demarcates distinct PT-symmetric phases: a unique configuration with coexisting broken and protected PT-symmetry regimes, tunable via the interplay of the traveling field strength and magnon-photon coupling. We also verify this by measuring the divergence around EP with Petermann Factor. Crucially, the system exhibits stable PT-symmetry only at specific field incidence angles, with instability or broken symmetry dominating elsewhere. Beyond PT-symmetry, we demonstrate robust quantum entanglement among the magnon, photon, and phonon subsystems. The exceptional point serves as a critical boundary, with unbroken and broken PT symmetry phases enabling dynamic entanglement swapping between subsystem pairs. By modulating the non-Hermitian parameters, we achieve controlled entanglement transfer and suppression of fluctuations, highlighting the system’s potential for quantum information processing. These results establish a direct connection between non-Hermitian topology, dynamical stability, and quantum correlations, providing a framework for leveraging PT symmetry in cavity magnomechanics for quantum technologies.
We propose a scheme to achieve nonreciprocal unconventional magnon blockade (NUMB) based on the Barnett and Sagnac effects in a hybrid nonlinear system, in which a microwave cavity with two modes and a yttrium iron garnet (YIG) sphere are included. Two cavity modes with the fundamental and the second-harmonic frequencies are coupled by virtue of the χ (2) nonlinear materials, and meanwhile, the fundamental mode interacts with the magnon mode via the magnetic dipole interaction. Under weak driving and coupling conditions, the magnon blockade is obtained, where the second-order correlation function has been used to analyze the magnon antibunching based on the numerical simulations and analytical calculations. The underlying mechanism is that quantum destructive interference occurs between different transition paths. In addition, the combination of the Barnett and Sagnac effects, which leads to the simultaneous frequency shifts of the magnon and two microwave modes, could induce the nonreciprocity of magnon antibunching due to the positive and negative detunings via changing the direction of the external fields. The scheme we present is based on the weak near-resonant coupling between quantum modes and the weak driving of magnon and photon modes, which may demonstrate the potential for achieving the single-magnon resource in a hybrid cavity magnonic system and provide valuable guidance for the design of nonreciprocal magnon devices.
We present an alternative scheme to achieve nonreciprocal unconventional magnon blockade (NUMB) in a hybrid system formed by two microwave cavities and one yttrium iron garnet (YIG) sphere, where the pump and signal cavities interact nonlinearly with each other and the signal cavity is coupled to the YIG sphere. It is found that the nonlinear coupling occurs between the pump cavity and magnon modes due to the dispersive interactions among three bosonic modes. Meanwhile, the Kerr nonlinearity is present in the pump cavity. Based on these nonlinear effects, a nonreciprocal magnon blockade could be achieved with the help of weak parametric driving of the pump cavity. The present work provides an alternative method to prepare single magnon resource, which may be helpful for quantum information processing.
We investigate unconventional magnon blockade (UMB) in a dissipative photon–magnon coupling cavity, where the coherent and dissipative coupling between photon and magnon can be adjusted by the position of the yttrium iron garnet sphere in the cavity. An approximate analytical solution for the statistical property of magnon is provided, which is in good agreement with the results obtained by numerically solving the Lindblad master equation. Our results indicate that UMB can be achieved in the case of dissipative photon–magnon coupling, but not in the case of coherent photon–magnon coupling. Secondly, by adjusting the amplitude of the external laser field, dynamic control of UMB can be achieved. Finally, by solving the Lindblad master equation containing the occupation number of thermal magnon and photon, the statistical properties of magnons will transition from nonclassical to classical. It is shown that the above phenomena originate from the interference between different quantum paths. Our research may provide theoretical possibilities for quantum manipulation schemes at the single-magnon level and open up a new avenue for designing single-magnon sources in a dissipative photon–magnon coupling system. • UMB can be generated by dissipative photon–magnon coupling, not coherent coupling. • The analytical optimal parameter for UMB is in agreement with the numerical result. • Dynamic-controlled UMB can be achieved by adjusting the external laser fields.