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TT: Fachverband Tiefe Temperaturen

TT 30: Superconductivity - Poster Session

TT 30.59: Poster

Montag, 31. März 2014, 15:00–19:00, P2

Ultrasonic saturation of tunneling systems in superconducting circuits — •Saskia Meißner, Lucas Radtke, Jochen Braumüller, Hannes Rotzinger, Martin Weides, Alexey V. Ustinov, and Georg Weiß — Physikalisches Institut, KIT Karlsruhe

Atomic two-level tunneling systems (TLS) are well known to dominate the thermodynamic low temperature properties of amorphous solids. They are formed by an atom or a group of atoms tunneling between two configurations within the disordered solid. These TLS are also present in the disordered thin oxide layer of capacitors in superconducting resonators or tunnel barriers in Josephson junctions in superconducting circuits where they are known as a source of dielectric loss and qubit decoherence.

The resonant part of the dielectric loss, caused by TLS with energies fitting the measurement frequency, can be saturated at sufficiently high microwave power due to the reduction of the TLS’s occupation number difference. Here we will exploit the coupling of the TLS to mechanical strain field to saturate them with high frequency ultrasonic waves.

The required ultrasonic waves in the GHz range are generated either by surface acoustic wave transducers directly integrated in the superconducting resonator circuit or by bulk acoustic wave transducers on the chip’s backside. RF-sputtered zinc oxide is used as piezoelectric film. Chip design, simulation of the resonators and data will be presented.