Berlin 2018 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 49: Superconductivity: Superconducting Electronics I

TT 49.6: Talk

Wednesday, March 14, 2018, 11:00–11:15, H 2053

Reconstructing Josephson current-phase relations from intermodulation spectroscopy — •Thomas Weißl, Shan W. Jolin, Per-Anders Thorén, Riccardo Borgani, Daniel Forchheimer, and David B. Haviland — KTH- Royal Institute of Technology, Stockholm, Sweden

Two pump tones driving a nonlinear system intermodulate, creating response at integer linear combinations of the their frequencies. With appropriate choice of the pumping frequencies, it is possible to measure not only the amplitudes, but also the phases of these intermodulation products, which depend on the detailed form of the nonlinearity that generates them. We present a method based on pseudo-inversion of a ’mixing matrix’ built from the intermodulation response, to reconstruct the non-linear current-phase relation of a superconducting weak link [1,2]. The intermodulation spectra of a Nb-coplanar waveguide resonator with an engineered weak-link was measured as a function of drive amplitude, and the method was applied to obtain the coefficients of a Taylor expansion of the current-phase relation. The method allows for precision characterization of nonlinearities in microwave crcuits without the need of DC connections.
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