Magnonic systems are a promising resource for quantum technologies because of their ability to couple significantly disparate quantum platforms and the generation of nonclassical magnon states through magnon blockade has attracted growing attention. In practice, however magnon blockade relies on a destructive interference that is easily spoiled by fabrication-induced coupling asymmetries. Here we show that the relative phase between two magnon drives acts as an active compensation knob that restores this interference even when the couplings are mismatched. We study two Kittel magnon modes in a hybrid system in which a superconducting qubit coupled to a common cavity mode mediates the inter-mode interaction and we find that tuning the drive phase produces both magnon blockade and a strong violation of the classical Cauchy--Schwarz inequality. We derive the analytic condition for the phase that compensates a given coupling asymmetry and confirm it against exact numerical simulations. The drive phase thereby serves as a control knob that switches the system between classical and quantum regimes. Our results enable phase-controlled magnonic quantum information processing.
Magnonic systems are a promising resource for quantum technologies because of their ability to couple significantly disparate quantum platforms and the generation of nonclassical magnon states through magnon blockade has attracted growing attention. In practice, however magnon blockade relies on a destructive interference that is easily spoiled by fabrication-induced coupling asymmetries. Here we show that the relative phase between two magnon drives acts as an active compensation knob that restores this interference even when the couplings are mismatched. We study two Kittel magnon modes in a hybrid system in which a superconducting qubit coupled to a common cavity mode mediates the inter-mode interaction and we find that tuning the drive phase produces both magnon blockade and a strong violation of the classical Cauchy--Schwarz inequality. We derive the analytic condition for the phase that compensates a given coupling asymmetry and confirm it against exact numerical simulations. The drive phase thereby serves as a control knob that switches the system between classical and quantum regimes. Our results enable phase-controlled magnonic quantum information processing.
We theoretically propose a magnon-based superconducting qubit hybrid system containing two ferromagnetic yttrium iron garnets (YIGs) and one superconducting qubit, demonstrating that this hybrid quantum system is feasible in achieving the unconventional two-mode magnon blockade and generating the quantum correlated magnon pairs. Through the virtual-photon excitation mediated by the same cavity mode, the effective couplings can be established not only between the Kittel modes and the qubit, but also between the two Kittel modes. We characterize the magnon blockade by utilizing the equal-time second-order correlation functions and impose a constraint on the correlations between the two Kittel modes by introducing the Cauchy-Schwarz inequality (CSI). In the weak qubit-magnon coupling regime, our results indicate the following: (i) Under the scenario of the resonance couplings, the ratio of driving strengths and the ratio of coupling strengths between the two Kittel modes and the cavity mode can be employed to control and regulate the magnon blockade and the violation of the CSI. Not only the two Kittel modes can achieve the unconventional magnon antibunching effects simultaneously, but also the correlations between them violate the classical CSI. It is important to note that when the degrees of both the antibunching effects for the two Kittel modes and the anticorrelation between them reach their highest levels simultaneously, the correlations happen not to violate the CSI. But our proposal offers a feasible route for preparing a high-quality single-magnon source. (ii) Under the scenario of the out-of-resonance couplings, by adjusting the frequency detunings between the first Kittel mode and the second Kittel mode as well as the qubit, the quantum correlated two-mode magnon pairs can be obtained. (iii) Finally, it is found that the magnon antibunching effect of the second Kittel mode is robust against the dissipation ratio between the two Kittel modes. These results illustrate how to optimally choose the parameters to realize nonclassical magnon pair generation and CSI violation. The hybrid YIG quantum system we propose here holds the potential in the development of efficient microwave single-magnon sources and quantum magnon-magnon pairs required in future quantum information processing tasks.
In this work, we study the phenomena of quantum-interference-assisted magnon blockade and magnon antibunching in a weakly interacting hybrid ferromagnet-superconductor system. The magnon excitations in two yttrium iron garnet spheres are indirectly coupled to a superconducting qubit through microwave cavity modes of two mutually perpendicular cavities. We find that when one of the magnon modes is driven by a weak microwave field, the destructive interference between more than two distinct transition pathways restricts the simultaneous excitation of two magnons. We analyze the magnon correlations in the driven magnon mode for the case of zero detunings as well as finite detunings of the magnon modes and the qubit. We show that the magnon antibunching can be tuned by changing the magnon-qubit coupling strength ratio and the driving detuning. Our work proposes a possible scheme that has a significant role in the construction of single magnon generating devices.
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 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.
We study the multimagnon blockade and magnon-induced tunneling in the hybrid ferromagnet-superconductor system, where a magnon mode representing the collective motion of spins in the yttrium iron garnet (YIG) sphere is coupled with a three-level $\mathrm{\ensuremath{\Delta}}$-type fluxonium qubit via the virtual-photon excitation from the microwave cavity. By appropriately choosing the parameters, the single magnon blockade, multimagnon blockade including two- and three-magnon blockades, and magnon-induced tunneling could be achieved. Fortunately, the switch from magnon blockade to magnon-induced tunneling could be obtained via controlling the overall phase of the loop transition determined by the driving fields. Furthermore, the single-magnon blockade could be transformed into a multimagnon blockade via the phase modulation. The scheme we present may provide an alternative method to manipulate the few-magnon states and have potential applications in quantum communication and quantum information processing.
In this paper, we propose a quantum interference mediated control of switching between magnon-atom entanglement and magnon blockade. A three-level $\mathrm{\ensuremath{\Lambda}}$ configuration atomic ensemble and a yttrium iron garnet sphere are simultaneously coupled to a microwave cavity mode through magnetic dipole interaction. By applying two strong fields to drive the atoms, the resonant coupling between a dressed-state atomic transition and the magnon mode, without direct interaction, is established by adiabatically eliminating the cavity field. Interestingly, the anti-Jaynes-Cummings (JC) interaction and the JC interaction are alternatively formed when the atoms are trapped into different superposition states induced by quantum interference, causing the appearance of hybrid magnon-atom entanglement and magnon quantum blockade, respectively. The coherent-controlled hybrid magnon-atom entanglement and magnon blockade may find potential applications in quantum information processing.