  Quantum information processing systems rely on a broad range of microwave
technologies and have spurred development of microwave devices and methods in
new operating regimes. Here we review the use of microwave signals and systems
in quantum computing, with specific reference to three leading quantum
computing platforms: trapped atomic ion qubits, spin qubits in semiconductors,
and superconducting qubits. We highlight some key results and progress in
quantum computing achieved through the use of microwave systems, and discuss
how quantum computing applications have pushed the frontiers of microwave
technology in some areas. We also describe open microwave engineering
challenges for the construction of large-scale, fault-tolerant quantum
computers.
