Solid state electrical circuits that behave as artificial quantum atoms are now fabricated for processing quantum information, and for addressing fundamental issues in quantum mechanics. I will describe how a simple superconducting artificial atom, the Cooper pair box, embedded in a microwave cavity just as atoms are in cavity QED physics, provides a playground for quantum mechanics and an operational quantum bit. In this talk, I will discuss some specific quantum physics experiments, and will give an overview of superconducting quantum processors. par In a single qubit circuit measured and driven at the same time, we have probed the violation of the Leggett and Garg inequality which falsifies the assumptions of macrorealism, considered as plausible for macroscopic systems such as electrical circuits [1]. With an elementary quantum processor [2], we have demonstrated the quantum speed-up of the Grover search algorithm. By coupling an ensemble of electronic spins and a qubit and to a same microwave cavity, we have demonstrated the operation of a quantum memory based on spin ensembles [3]. \ \ {} [1] A. Palacios-Laloy, et al. Nature Phys. 6, 442-447 (2010). \ {} [2] A. Dewes et al., Phys. Rev. Lett. 108, 057002 (2012) & Phys. Rev. B 85, 140503 (2012). \ {} [3] Y. Kubo et al., Phys. Rev. Lett. 107, 220501(2011).