Conventional and unconventional magnon blockades in a qubit-magnon hybrid quantum system

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.