Cavity quantum electrodynamics with atom-like mirrors

• Published in: Nature (London) 2019-05, Vol.569 (7758), p.692-697
• Main Authors: Mirhosseini, Mohammad, Kim, Eunjong, Zhang, Xueyue, Sipahigil, Alp, Dieterle, Paul B., Keller, Andrew J., Asenjo-Garcia, Ana, Chang, Darrick E., Painter, Oskar
• Format: Article
• Language: English
• Subjects: 142/126; 639/766/36/1121; 639/766/483/2802; 639/766/483/3925; Analysis; Control; Coupling; Dissipation; Electrodynamics; Electrons; Emissions; Emitters; Humanities and Social Sciences; Letter; Mirrors; multidisciplinary; Optical waveguides; Physics; Quantum dots; Quantum electrodynamics; Qubits (quantum computing); Radiation; Science; Science (multidisciplinary); Spontaneous emission; Subspaces; Superconducting quantum interference devices; Waveguides
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-019-1196-1

It has long been recognized that atomic emission of radiation is not an immutable property of an atom, but is instead dependent on the electromagnetic environment 1 and, in the case of ensembles, also on the collective interactions between the atoms 2 – 6 . In an open radiative environment, the hallmark of collective interactions is enhanced spontaneous emission—super-radiance 2 —with non-dissipative dynamics largely obscured by rapid atomic decay 7 . Here we observe the dynamical exchange of excitations between a single artificial atom and an entangled collective state of an atomic array 9 through the precise positioning of artificial atoms realized as superconducting qubits 8 along a one-dimensional waveguide. This collective state is dark, trapping radiation and creating a cavity-like system with artificial atoms acting as resonant mirrors in the otherwise open waveguide. The emergent atom–cavity system is shown to have a large interaction-to-dissipation ratio (cooperativity exceeding 100), reaching the regime of strong coupling, in which coherent interactions dominate dissipative and decoherence effects. Achieving strong coupling with interacting qubits in an open waveguide provides a means of synthesizing multi-photon dark states with high efficiency and paves the way for exploiting correlated dissipation and decoherence-free subspaces of quantum emitter arrays at the many-body level 10 – 13 . An array of superconducting qubits in an open one-dimensional waveguide is precisely controlled to create an artificial quantum cavity–atom system that reaches the strong-coupling regime without substantial decoherence.