  The aim of this review is to provide quantum engineers with an introductory
guide to the central concepts and challenges in the rapidly accelerating field
of superconducting quantum circuits. Over the past twenty years, the field has
matured from a predominantly basic research endeavor to one that increasingly
explores the engineering of larger-scale superconducting quantum systems. Here,
we review several foundational elements -- qubit design, noise properties,
qubit control, and readout techniques -- developed during this period, bridging
fundamental concepts in circuit quantum electrodynamics (cQED) and
contemporary, state-of-the-art applications in gate-model quantum computation.
