2017/02/28 by Naftali Kirsh, Elisha Svetitsky, Alexander L. Burin +2
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevmaterials.1.012601
published as Phys. Rev. Materials 1, 012601 (2017) · 6 pages, 4 figures + supplementary (with 18 pages and 5 figures)
arxiv created 2017/07/02 · arxiv updated 2017/07/05
Atomic sized two-level systems (TLSs) in amorphous dielectrics are known as a major source of loss in superconducting devices. In addition, individual TLS 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 life-time of each resonance can be controlled (increased) by pumping of the other mode as demonstrated both experimentally and theoretically.