Using modern micro and nano-fabrication techniques combined with superconducting materials we realize quantum electronic circuits. We create, store, and manipulate individual microwave photons on chip. The strong interaction of photons with superconducting quantum two-level systems allows us to probe fundamental quantum effects of light and also to develop components for applications in quantum information technology. In this presentation, I will discuss how we realize an on-demand single photon source which we characterize using correlation function measurements [1,2] and full quantum state tomography . For this purpose we have developed efficient methods to separate the quantum signals of interest from the noise added by the linear amplifiers used for quadrature amplitude detection . We now regularly employ our own superconducting parametric amplifiers  to perform nearly quantum limited detection of propagating electromagnetic fields. These enable us to probe the entanglement which we generate on demand between stationary qubits and microwave photons freely propagating down a transmission line . The non-local nature of these states may prove to be useful for distributing entanglement in future small-scale quantum networks. Using two independent microwave single photon sources, we have also performed first Hong-Ou-Mandel experiments and have probed the coherence of two-mode multi-photon states at the out-put of the beam-splitter.
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