  The article is a short opinionated review of the quantum treatment of
electromagnetic circuits, with no pretension to exhaustiveness. This review,
which is an updated and modernized version of a previous set of Les Houches
School lecture notes, has 3 main parts. The first part describes how to
construct a Hamiltonian for a general circuit, which can include dissipative
elements. The second part describes the quantization of the circuit, with an
emphasis on the quantum treatment of dissipation. The final part focuses on the
Josephson non-linear element and the main linear building blocks from which
superconducting circuits are assembled. It also includes a brief review of the
main types of superconducting artificial atoms, elementary multi-level quantum
systems made from basic circuit elements.
