  A quantum network consisting of magnonic and mechanical nodes connected by
light is proposed. Recent years have witnessed a significant development in
cavity magnonics based on collective spin excitations in ferrimagnetic
crystals, such as yttrium iron garnet (YIG). Magnonic systems are considered to
be a promising building block for a future quantum network. However, a major
limitation of the system is that the coherence time of the magnon excitations
is limited by their intrinsic loss (typically in the order of 1 $\mu$s for
YIG). Here, we show that by coupling the magnonic system to a mechanical system
using optical pulses, an arbitrary magnonic state (either classical or quantum)
can be transferred to and stored in a distant long-lived mechanical resonator.
The fidelity depends on the pulse parameters and the transmission loss. We
further show that the magnonic and mechanical nodes can be prepared in a
macroscopic entangled state. These demonstrate the quantum state transfer and
entanglement distribution in such a novel quantum network of magnonic and
mechanical nodes. Our work shows the possibility to connect two separate fields
of optomagnonics and optomechanics, and to build a long-distance quantum
network based on magnonic and mechanical systems.
