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arXiv · 0810.0590

One- and two-photon spectroscopy of a flux qubit coupled to a microscopic defect

A. Lupascu·P. Bertet·E. F. C. Driessen·C. J. P. M. Harmans·J. E. Mooij
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Abstract

We observed the dynamics of a superconducting flux qubit coupled to an extrinsic quantum system (EQS). The presence of the EQS is revealed by an anticrossing in the spectroscopy of the qubit. The excitation of a two-photon transition to the third excited state of the qubit-EQS system allows us to extract detailed information about the energy level structure and the coupling of the EQS. We deduce that the EQS is a two-level system, with a transverse coupling to the qubit. The transition frequency and the coupling of the EQS changed during experiments, which supports the idea that the EQS is a two-level system of microscopic origin.

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A. Lupascu, P. Bertet, E. F. C. Driessen, C. J. P. M. Harmans, J. E. Mooij. 2008-10-03. One- and two-photon spectroscopy of a flux qubit coupled to a microscopic defect. https://doi.org/10.1103/physrevb.80.172506

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