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arXiv · 1412.7372

Ultrastrong coupling in two-resonator circuit QED

A. Baust·E. Hoffmann·M. Haeberlein·M. J. Schwarz·P. Eder·J. Goetz·F. Wulschner·E. Xie·L. Zhong·F. Quijandria·D. Zueco·J. -J. Garcia Ripoll·L. Garcia-Alvarez·G. Romero·E. Solano·K. G. Fedorov·E. P. Menzel·F. Deppe·A. Marx·R. Gross
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Abstract

We report on ultrastrong coupling between a superconducting flux qubit and a resonant mode of a system comprised of two superconducting coplanar stripline resonators coupled galvanically to the qubit. With a coupling strength as high as 17% of the mode frequency, exceeding that of previous circuit quantum electrodynamics experiments, we observe a pronounced Bloch-Siegert shift. The spectroscopic response of our multimode system reveals a clear breakdown of the Jaynes-Cummings model. In contrast to earlier experiments, the high coupling strength is achieved without making use of an additional inductance provided by a Josephson junction.

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A. Baust, E. Hoffmann, M. Haeberlein, M. J. Schwarz, P. Eder, J. Goetz, F. Wulschner, E. Xie, L. Zhong, F. Quijandria, D. Zueco, J. -J. Garcia Ripoll, L. Garcia-Alvarez, G. Romero, E. Solano, K. G. Fedorov, E. P. Menzel, F. Deppe, A. Marx, R. Gross. 2014-12-23. Ultrastrong coupling in two-resonator circuit QED. https://doi.org/10.1103/physrevb.93.214501

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