We investigate magnon statistics in a qubit-magnon hybrid quantum system in which an effective appreciable qubit-magnon coupling can be realized by exchanging virtual cavity photons. A conventional magnon blockade and two types of unconventional magnon blockades are proposed, respectively, based on three different physical mechanisms. We verify theoretically that a magnon blockade can occur in strong, weak, and moderate qubit-magnon coupling regimes. It is interesting that an asymmetry structure for magnon anti-bunching can be observed in the case of the moderate qubit-magnon coupling strength, especially where the quantum interference can significantly relax the requirement of the larger coupling strength between the qubit and magnon mode. All of the approximate analytical results for strong magnon anti-bunching are in good agreement with those obtained by numerical simulations. Our results provide a promising pathway for coherent manipulation in single magnon level, which has potential applications for quantum information processing and preparation of single magnon sources.
We investigate magnon statistics in a qubit-magnon hybrid quantum system in which an effective appreciable qubit-magnon coupling can be realized by exchanging virtual cavity photons. A conventional magnon blockade and two types of unconventional magnon blockades are proposed, respectively, based on three different physical mechanisms. We verify theoretically that a magnon blockade can occur in strong, weak, and moderate qubit-magnon coupling regimes. It is interesting that an asymmetry structure for magnon anti-bunching can be observed in the case of the moderate qubit-magnon coupling strength, especially where the quantum interference can significantly relax the requirement of the larger coupling strength between the qubit and magnon mode. All of the approximate analytical results for strong magnon anti-bunching are in good agreement with those obtained by numerical simulations. Our results provide a promising pathway for coherent manipulation in single magnon level, which has potential applications for quantum information processing and preparation of single magnon sources.
Abstract Magnon blockade (MB) is a fundamental quantum phenomenon for generating single-magnon states, and has gradually become one of the candidates for quantum information processing. We extend existing blockade optimization schemes to a hybrid system consisting of a YIG micromagnet and a skyrmion, and propose a theoretical scheme for achieving MB on this platform. Under weak magnon probing and external driving of the skyrmion qubit, the second-order correlation function is analytically derived, and the optimal parameter conditions for both conventional and unconventional MB are identified. By appropriately adjusting the intensities of the driving and probing fields, the MB effect is significantly enhanced, multi-magnon excitations are effectively suppressed, and strong antibunching is achieved. Further analysis reveals that MB originates from two distinct physical mechanisms: conventional blockade induced by anharmonicity of the energy level structure, and unconventional blockade arising from quantum interference between different transition paths. On this platform, the two mechanisms coexist and can be synergistically controlled, and their cooperation yields a blockade effect superior to that of either mechanism alone. This work thus provides a feasible theoretical scheme for the effective manipulation of MB effects.
Magnon blockade is a physical mechanism for the preparation of a single-magnon source, which has important applications in quantum information processing. Here we propose a scheme for generating an optimal magnon blockade in the spin-magnon quantum system. By introducing frequency detuning between the magnon and the spin qubit of the NV center, the conventional magnon blockade and the unconventional magnon blockade can be obtained under both strong and weak coupling, relaxing the requirements for coupling strength. Moreover, the conventional and unconventional magnon blockade can occur simultaneously when both the magnon and the spin qubit are driven. This allows the equal-time second-order correlation function to reach 10−8, about five orders of magnitude lower than that in previous works. Additionally, the time-delayed second-order correlation function avoids oscillation. Our study demonstrates the impact of frequency detuning on the magnon blockade and proposes methods to enhance the magnon blockade and relax the requirements for coupling strength through frequency detuning.
We explore a scheme to investigate the tunable magnon antibunching characteristics of the conventional magnon blockade (CMB) and the unconventional magnon blockade (UMB) in a hybrid ferromagnet-superconductor system. The magnon excited in the yttrium iron garnet is indirectly coupled to two qubits by eliminating two mutually perpendicular microwave cavity modes. In our paper, we relax the magnon-qubits detuning constraint. In two cases with and without magnon-qubits detuning, it is found that in the strong coupling regime CMB and UMB coexist in our system, and they can be regulated simultaneously by varying the magnon-qubits coupling strength ratio and the qubits detuning ratio. In the weak coupling regime, there exists only the UMB in the system. Without magnon-qubits detuning, the UMB shows a nonmonotonic dependence on the magnon-qubits coupling strength ratio. With magnon-qubits detuning, for the UMB, the magnon bunching effect and antibunching effect can be converted mutually by adjusting the magnon-qubits coupling strength ratio and the qubits detuning ratio. Moreover, changing the magnon-qubits coupling strength ratio and the qubits detuning ratio has a significant impact on the antibunching effect against the thermal magnon excitation. Our research results provide a theoretical scheme for the manipulation of magnon antibunching characteristics, and have important practical significance for the construction of a single magnon source.
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.
Abstract We study the magnon antibunching effect in the magnon-qubit coupling system under the joint action of coherent and parametric drives. The analysis and numerical results reveal the conventional magnon blockade (CMB) caused by the anharmonic level splitting induced by strong magnon–qubit coupling and the unconventional magnon blockade (UMB) induced by multipath destructive interference. Notably, in the strong-coupling regime, substituting the CMB condition into the optimal UMB condition yields a phase-tuned CMB-constrained UMB condition, which simultaneously realizes strong magnon antibunching and a high single-magnon occupation probability. This combines the high brightness afforded by CMB with the high purity provided by UMB. Furthermore, in the weak-coupling regime, coordinated tuning of the phase, detuning, parametric drive, and coupling strength induces destructive interference among distinct excitation pathways, thereby yielding the UMB effect. Importantly, even in the zero-coupling limit, the additional channel provided by the parametric drive can sustain this blockade. This flexibility removes the reliance on stringent strong-coupling constraints, offering a viable route toward tunable strong magnon antibunching.
A hybrid system established by the direct interaction between a magnon mode and a superconducting transmon qubit is used to realize a high-degree blockade for magnon. It is a fundamental way toward quantum manipulation at the level of a single magnon and preparation of single magnon sources. Through weakly driving the magnon and probing the qubit, our magnon-blockade proposal can be optimized when the transversal coupling strength between the magnon and qubit is equivalent to the detuning of the qubit and the probing field or that of the magnon and the driving field. Under this condition, the equal-time second-order correlation function g(2)(0) can be analytically minimized when the probing intensity is about three times the driving intensity. Moreover, the magnon blockade could be further enhanced by proper driving intensity and system decay rate, whose magnitudes outrange the current systems of cavity QED and cavity optomechanics. In particular, the correlation function achieves ${g}^{(2)}(0)\ensuremath{\sim}{10}^{\ensuremath{-}7}$, about two orders lower than that for the photon blockade in cavity optomechanics. Also, we discuss the effects on g(2)(0) from thermal noise and the extra longitudinal interaction between the magnon and qubit. Our optimized conditions for blockade are found to persist in these nonideal situations.