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Ultrastrong coupling of a single artificial atom to an electromagnetic continuum in the nonperturbative regime

Nature Physics volume 13, pages 39–43 (2017)Cite this article

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Abstract

The study of light–matter interaction has led to important advances in quantum optics and enabled numerous technologies. Over recent decades, progress has been made in increasing the strength of this interaction at the single-photon level. More recently, a major achievement has been the demonstration of the so-called strong coupling regime1,2, a key advancement enabling progress in quantum information science. Here, we demonstrate light–matter interaction over an order of magnitude stronger than previously reported, reaching the nonperturbative regime of ultrastrong coupling (USC). We achieve this using a superconducting artificial atom tunably coupled to the electromagnetic continuum of a one-dimensional waveguide. For the largest coupling, the spontaneous emission rate of the atom exceeds its transition frequency. In this USC regime, the description of atom and light as distinct entities breaks down, and a new description in terms of hybrid states is required3,4. Beyond light–matter interaction itself, the tunability of our system makes it a promising tool to study a number of important physical systems, such as the well-known spin-boson5 and Kondo models6.

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Figure 1: Measurement set-up and devices.
Figure 2: Spectroscopy of devices with fixed coupling.
Figure 3: Tunable ultrastrong coupling device.
Figure 4: Normalized coupling rates and frequency renormalization.

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Acknowledgements

We acknowledge financial support from NSERC of Canada, the Canadian Foundation for Innovation, the Ontario Ministry of Research and Innovation, Industry Canada, Canadian Microelectronics Corporation, EU FP7 FET-Open project PROMISCE, Spanish Mineco Project FIS2012-33022 and CAM Network QUITEMAD+. B.P. acknowledges the Air Force of Scientific Research for support under award FA9550-12-1-0046. The University of Waterloo’s Quantum NanoFab was used for this work. We thank A. J. Leggett and A. Garg for fruitful discussions, and M. Otto, S. Chang, A. M. Vadiraj and C. Deng for help with device fabrication and with the measurement set-ups.

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Author notes

  1. C. M. Wilson and A. Lupascu: These authors contributed equally to this work.

Authors and Affiliations

  1. Institute for Quantum Computing, University of Waterloo, Waterloo N2L 3G1, Canada

    P. Forn-Díaz, J.-L. Orgiazzi, M. A. Yurtalan, R. Belyansky, C. M. Wilson & A. Lupascu

  2. Department of Physics and Astronomy, University of Waterloo, Waterloo N2L 3G1, Canada

    P. Forn-Díaz & A. Lupascu

  3. Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo N2L 3G1, Canada

    P. Forn-Díaz, J.-L. Orgiazzi, M. A. Yurtalan & A. Lupascu

  4. Instituto de Física Fundamental IFF-CSIC, Madrid 28006, Spain

    J. J. García-Ripoll

  5. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA

    B. Peropadre

  6. Department of Electrical and Computer Engineering, University of Waterloo, Waterloo N2L 3G1, Canada

    J.-L. Orgiazzi, M. A. Yurtalan, R. Belyansky & C. M. Wilson

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  1. P. Forn-Díaz
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Contributions

P.F.-D., C.M.W. and A.L. designed the experiment. P.F.-D. designed the devices and fabricated them. P.F.-D., C.M.W. and A.L. conducted the experiments. J.-L.O. provided input to device design and fabrication. M.A.Y. and R.B. assisted in numerical modelling of devices. J.J.G.-R. and B.P. provided theoretical support to interpret the measurements. P.F.-D., C.M.W. and A.L. performed the data analysis and wrote the manuscript with feedback from all authors. C.M.W. and A.L. supervised the project.

Corresponding authors

Correspondence to P. Forn-Díaz, C. M. Wilson or A. Lupascu.

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The authors declare no competing financial interests.

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Forn-Díaz, P., García-Ripoll, J., Peropadre, B. et al. Ultrastrong coupling of a single artificial atom to an electromagnetic continuum in the nonperturbative regime. Nature Phys 13, 39–43 (2017). https://doi.org/10.1038/nphys3905

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