  Quantum technology has made tremendous strides over the past two decades with
remarkable advances in materials engineering, circuit design and dynamic
operation. In particular, the integration of different quantum modules has
benefited from hybrid quantum systems, which provide an important pathway for
harnessing the different natural advantages of complementary quantum systems
and for engineering new functionalities. This review focuses on the current
frontiers with respect to utilizing magnetic excitatons or magnons for novel
quantum functionality. Magnons are the fundamental excitations of magnetically
ordered solid-state materials and provide great tunability and flexibility for
interacting with various quantum modules for integration in diverse quantum
systems. The concomitant rich variety of physics and material selections enable
exploration of novel quantum phenomena in materials science and engineering. In
addition, the relative ease of generating strong coupling and forming hybrid
dynamic systems with other excitations makes hybrid magnonics a unique platform
for quantum engineering. We start our discussion with circuit-based hybrid
magnonic systems, which are coupled with microwave photons and acoustic
phonons. Subsequently, we are focusing on the recent progress of magnon-magnon
coupling within confined magnetic systems. Next we highlight new opportunities
for understanding the interactions between magnons and nitrogen-vacancy centers
for quantum sensing and implementing quantum interconnects. Lastly, we focus on
the spin excitations and magnon spectra of novel quantum materials investigated
with advanced optical characterization.
