# IQIM Postdoctoral and Graduate Student Seminar

*,*John G Braun Professor of Applied Physics and Physics; Fletcher Jones Foundation Co-Director of the Kavli Nanoscience Institute

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**Abstract**: The complexity and emergent behavior of a many-body quantum system is intimately related to the connectivity of its constituent quantum elements. In the case of Josephson junction qubits and superconducting quantum circuits, connectivity between qubits can be realized using a myriad of techniques. Near-field interactions, through capacitive or inductive components, can be used to realize local connections. Microwave resonators with closed electromagnetic boundaries, like that in a 3-dimensional superconducting box cavity, can provide all-to-all coupling between qubits, albeit typically (single-mode case) in a manner that results in a system with effectively 0 spatial dimensions. Nontrivial long-range interactions, however, can be mediated in a superconducting microwave circuit using waveguides which channel microwave radiation. Waveguide quantum electrodynamics (QED), which explores the interactions of quantum emitters with the continuum of electromagnetic modes of a one-dimensional radiation channel, is thus a natural setting in which to consider the emergent physics that may be possible using superconducting quantum circuits. In this talk I will describe two waveguide QED experiments that we have recently performed, one involving strong dispersion in engineered metamaterial waveguides and the other probing coherent dynamics arising from photon-mediated interactions between distant qubits connected along a common waveguide. From these two experiments, I will also chart a course for future experiments that would allow us to study many-body interactions and open quantum system dynamics in the non-Markovian limit.

**Note location for this week only: Talk will be in 105 Annenberg**