Waveguide Quantum Electrodynamics with Artificial Atoms

The strong-coupling regime of atom-photon interactions, in which a single atom and single photon can coherently exchange an excitation, is a common target for quantum optics and quantum information platforms. This is now readily achieved in cavity Quantum Electrodynamics (QED) by confining real or artificial atoms within the modes of cavities. There is a complementary paradigm, dubbed waveguide QED, where instead atoms couple to itinerant photons propagating in waveguides. The small mode volume of the waveguide can enable the strong-coupling regime even without cavity enhancement. In this talk, we discuss waveguide QED experiments using superconducting artificial atoms coupled to microwave coplanar waveguides, and we demonstrate the deterministic emission of a photon into a chosen direction. This scheme is a potential building block for remote entanglement or quantum communication protocols, and we will present experimental progress towards those goals.