Revealing the nonlinear response of a tunneling two-level system ensemble using coupled modes

Naftali Kirsh, Elisha Svetitsky, Alexander L. Burin, Moshe Schechter, Nadav Katz

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Atomic sized two-level systems (TLSs) in amorphous dielectrics are known as a major source of loss in superconducting devices. In addition, individual TLSs are known to induce large frequency shifts due to strong coupling to the devices. However, in the presence of a broad ensemble of TLSs these shifts are symmetrically canceled out and not observed in a typical single-tone spectroscopy experiment. We introduce a two-tone spectroscopy on the normal modes of a pair of coupled superconducting coplanar waveguide resonators to reveal this effect. Together with an appropriate saturation model this enables us to extract the average single-photon Rabi frequency of dominant TLSs to be Ω0/2π≈79 kHz. At high photon numbers we observe an enhanced frequency shift due to nonlinear kinetic inductance when using the two-tone method and estimate the value of the nonlinear coefficient as K/2π≈-1×10-4 Hz/photon. Furthermore, the lifetime of each resonance can be controlled (increased) by pumping of the other mode as demonstrated both experimentally and theoretically.

Original languageAmerican English
Article number012601
JournalPhysical Review Materials
Issue number1
StatePublished - 26 Jun 2017

Bibliographical note

Funding Information:
We thank Dr. Sebastian Probst and Prof. Lazar Friedland for fruitful discussions. A.L.B. acknowledges support from BGU and National Science Foundation (CHE-1462075) for partial support. M.S. acknowledges financial support from the Israel Science Foundation (Grant No. 821/14). This work is supported by the European Research Council Project No. 335933.

Publisher Copyright:
© 2017 American Physical Society.


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