  The new and rapidly growing field of circuit QED offers extremely exciting
prospects for learning about and exercising intimate control over quantum
systems, providing flexible, engineerable design and strong nonlinearities and
interactions in systems consisting of microwave radiation fields and fixed
artificial "atoms". These notes aim to provide a non-expert introduction to the
field of circuit QED, to give a basic appreciation of the promise and
challenges of the field, along with a number of key concepts that will
hopefully be useful for the reader who is new to the field and beginning to
explore the research literature. They were written as a pedagogical text
designed to complement a course delivered to third-year undergraduate students.
  After a introductory section which discusses why studying circuit QED might
be worthwhile and interesting, I introduce the basic theory tools from quantum
optics and quantum information which are needed to understand the key elements
of circuit QED. I also provide a brief overview of superconductivity, focussing
on the concepts which are most relevant to operation in the regimes of interest
in circuit QED. I then describe the three main types of superconducting qubits,
and finally give a basic introduction to decoherence and mixture and how they
relate to quantum behaviour in electronic circuits.
