INTERACTING PHOTONS IN CIRCUIT QUANTUM ELECTRODYNAMICS: DECAY OF THE COLLECTIVE PHASE MODE IN ONE-DIMENSIONAL JOSEPHSON JUNCTION ARRAYS DUE TO QUANTUM PHASE-SLIP FLUCTUATIONS
Grabon, Nicholas Christopher
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Light does not typically scatter light, as witnessed by the linearity of Maxwell’s equations. In this work, we demonstrate two superconducting circuits, in which microwave photons have well-defined energy and momentum, but their lifetime is finite due to decay into lower energy photons. The circuits we present are formed with Josephson junction arrays where strong quantum phase-slip fluctuations are present either in all of the junctions or in only a single junction. The quantum phase-slip fluctuations are shown to result in the strong inelastic photon-photon interaction observed in both circuits. The phenomenon of a single photon decay provides a new way to study multiple long-standing many-body problems important for condensed matter physics. The examples of such problems, which we cover in this work include superconductor to insulator quantum phase transition in one dimension and a general quantum impurity problem. The photon lifetime data can be treated as a rare example of a verified and useful quantum many-body simulation.