# IQIM Postdoctoral and Graduate Student Seminar

**Abstract**: Atoms and photons interact in free space in one of nature's most elemental processes. The dipolar interaction strength between the two systems is determined by fundamental constants, with one of its limiting factors being the mode volume of the propagating photons. A waveguide is an engineered medium that confines the electromagnetic field and in proximity to atoms allows light-matter interactions with stronger couplings compared to free space. In superconducting quantum circuits it is possible to study quantum electrodynamics with a transmission line on a chip replacing the waveguide and a superconducting qubit playing the role of an artificial atom. By proper engineering of these circuits, a wide range of possibilities opens up: from atom-photon interactions in unexplored regimes to wide band single-photon generation. In this talk, I am going to present recent experimental progress coupling qubits to open transmission lines. I will show results from an on-demand single photon source engineered using a tunable boundary condition in a semi-infinite transmission line, and the peculiar Lamb shifts occurring in the qubit frequency due to this tunable interaction. This work is relevant for the development of microwave quantum networks using superconducting qubits and it can be extended to other types of solid-state quantum systems, including resonators.

References:

I. C. Hoi et al., Nature Physics 11, 1045 (2015)

P. Forn-Diaz, et al., arxiv:1706.06688 (2017)