Controllable antibunching of two-magnon bundle in a hybrid ferromagnet-superconductor system.

We propose an alternative scheme for implementing the antibunching effects of two-magnon bundle in a hybrid ferromagnet-superconductor system, where a magnon mode from the yttrium iron garnet (YIG) sphere interacts with a three-level superconducting qubit via photon virtual excitation in the microwave cavity. With the help of the qubit driving from the ground state to the excited state, the cascaded emission of magnon occurs and then the two-magnon bundle is formed. By analyzing the ordinary and generalized second-order correlation functions, it is found that the antibunched two-magnon bundle could be achieved via properly choosing the system parameters, which is originated from the anharmonicity of dressed energy levels induced by magnon-qubit couplings. The distinct feature is that high-proportion n-magnon emission could be obtained via relaxing the restriction on the strong qubit driving and magnon-qubit coupling, which may provide a feasible method to realize the high-quality multimagnon source for quantum metrology and quantum information processing.