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Abstract

The dielectric loss of amorphous materials along with noise and decoherence are the major limiting factors for many applications at low temperatures like superconducting circuits, Josephson junctions and quantum computing. These effects are nowadays understood as the consequence of an ensemble of quantum mechanical two-level systems (TLSs), which are described as additional broadly distributed low-energy excitations in the sample. In this context, the thesis at hand presents a unique property of an amorphous material when two pump-tones are applied. In this limit the utilized LC-resonator is emitting at the intermediate frequency of the two off-resonant driving fields. The underlying mechanism can be explained by a non-linear interaction of the rf-field with the TLSs and the resonator, which creates additional lines in the frequency spectrum and thereby a self-biasing effect. The corresponding measurements also define a specific set of parameters for the occurrence of this emission limit, which is well described by a phenomenological approach in the context of the Landau-Zener-Stückelberg formalism. The obtained results thus complement the bigger picture of TLSs and open up a new approach for further investigations.