Radiative properties of an artificial atom coupled to a Josephson-junction array

Kanu Sinha, Saeed A. Khan, Elif Cüce, Hakan E. Türeci

Research output: Contribution to journalArticlepeer-review

Abstract

We study the radiative properties - the Lamb shift, Purcell decay rate, and spontaneous emission dynamics - of an artificial atom coupled to a long, multimode cavity formed by an array of Josephson junctions. Introducing a tunable coupling element between the atom and the array, we demonstrate that such a system can exhibit a crossover from a perturbative to a nonperturbative regime of light-matter interaction as one strengthens the coupling between the atom and the Josephson-junction array. As a consequence, the concept of spontaneous emission as the occupation of the local atomic site being governed by a single complex-valued exponent breaks down. This breakdown, we show, can be interpreted in terms of formation of hybrid atom-resonator modes with radiative losses that are nontrivially related to the effective coupling between individual modes. We develop a singular function expansion approach for the description of the open quantum system dynamics in such a multimode nonperturbative regime. This modal framework generalizes the normal-mode description of quantum fields in a finite volume, incorporating exact radiative losses and incident quantum noise at the delimiting surface. Our results are pertinent to recent experiments with Josephson atoms coupled to high-impedance Josephson-junction arrays.

Original languageEnglish (US)
Article number033714
JournalPhysical Review A
Volume106
Issue number3
DOIs
StatePublished - Sep 2022

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics

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