Magnon cat states induced by photon parametric coupling

Cat state, is not only interesting for testing the fundamentals of quantum mechanics, but also for wide applications ranging from fault-tolerant quantum computation to quantum metrology. Here, we propose a scheme to generate the magnon cat state by the indirect magnon nonlinearity. We show that the effective two-magnon loss process can be induced by the photon parametric coupling, steering the magnon into the cat-state manifold. In our work, the size of the magnon cat state can be easily adjusted, and the large-size cat state can be generated with high fidelity. At the same time, the speed of cat-state generation can be greatly improved by enhancing the photon-magnon interaction with maintaining a larger size of cat state. Further, we find that the effective two-magnon loss process can strongly suppress the decoherence of the environment under appropriate parameter conditions. The lifetime of the magnon cat state can be expected to be t~30.2em0exμs under the current experimental techniques. This work provides a proposal for the preparation of nonclassical states of magnons without the direct magnon nonlinearity, which is meaningful for the development of quantum technology in the future.