Running summarizing tools on a new article

Abstract: This appendix provide a self-contained presentation of the open systems and quantum optics methods used in other parts of the book (e.g., studying the relaxation of a microwave cavity or a qubit, the driving of a quantum amplifier, etc.). Half of the appendix is devoted to the derivation of master equations for small systems that are in contact with Markovian environments. The other half of the appendix is devoted to the development of an alternative input–output description of how those systems absorb information from the environment and reflect it back.