The research proposed in this application has grown out of the research on solid-state qubits, where a superconducting circuit including Josephson junctions can be made into a quantum-coherent, two-level system, an artificial atom. It has recently been shown that these artificial atoms can be integrated with microwave cavities in such a way that the states of the "atom" can communicate in a quantum coherent way with individual photons in the cavity. This opens up an opportunity to engineer quantum system utilizing both the atom and the photon degree of freedom. There are three essential features in this proposal, circuit-QED, tunable Josephson elements and the possibility to integrate many qubits and many cavities on the same chip. The overall objective of this proposal is to build a toolbox based on circuit-QED and tunable superconducting elements, to enable on-chip integrated quantum optics. Our vision is to move quantum optics experiments from large optical tables and integrate them on chip, with a substantially increased level of integration. Working in the microwave domain, we have the following specific objectives: " An on-demand single photon source " A number resolving single photon click detector " A single photon router " A single photon sluice " A linear quantum limited parametric amplifier " Demonstration of the dynamical Casimir effect