Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 33: Nonequilibrium Quantum Many-Body Systems (joint session TT/DY)

TT 33.1: Talk

Thursday, September 8, 2022, 15:00–15:15, H22

Investigating the non-equilibrium dynamics of two-level systems at low temperature — •Marcel Haas, Mareike Dinger, Lukas Münch, Jan Blickberndt, Andreas Reiser, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg, Germany

The dielectric loss of amorphous materials along with noise and decoherence is the major limiting factor in many applications like superconducting circuits, Josephson junctions and quantum computing. It is mainly determined by atomic tunneling systems described by quantum mechanical two-level systems (TLS), which are broadly distributed low-energy excitations in the sample. The spontaneous phonon emission of an excited TLS gives rise to a relaxation time T₁ and the interaction between TLSs with their thermally excited surrounding induces a decoherence time T₂. These effects mainly determine the measurable dielectric loss in the observed material, which we ascertain by measuring the quality factor of a bridge type superconducting LC-resonator. The dielectric medium in between the capacitor plates is a sputter deposited a-SiO₂ film. The setup shows a unique property when two off-resonant pump tones are applied symmetrically. In this limit, the resonator is emitting at the intermediate frequency of the driving fields. The underlying mechanism can therefore be explained by a nonlinear interaction of the rf-field with the TLSs and the resonator which is creating additional lines in the frequency spectrum. We present first measurements at a frequency of 1 GHz performed with a micro-fabricated superconducting resonator.