Probing the density of states of two-level tunneling systems in silicon oxide films using superconducting lumped element resonators

We have investigated dielectric losses in amorphous silicon oxide (a-SiO) thin films under operating conditions of superconducting qubits (mK temperatures and low microwave powers). For this purpose, we have developed a broadband measurement setup employing multiplexed lumped element resonators usin...

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Bibliographic Details
Published in:Applied physics letters 2015-01, Vol.106 (2)
Main Authors: Skacel, S. T., Kaiser, Ch, Wuensch, S., Rotzinger, H., Lukashenko, A., Jerger, M., Weiss, G., Siegel, M., Ustinov, A. V.
Format: Article
Language:English
Subjects:
Amorphous silicon
AMPLIFIERS
Applied physics
Broadband
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
DENSITY OF STATES
Dielectric loss
DIELECTRIC MATERIALS
ENERGY DEPENDENCE
MICROWAVE RADIATION
NOISE
OPERATION
Oxide coatings
Power combiners
PROBES
Quantum theory
QUBITS
RESONATORS
SILICON OXIDES
SUPERCONDUCTIVITY
THIN FILMS
TUNNEL EFFECT
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Summary:We have investigated dielectric losses in amorphous silicon oxide (a-SiO) thin films under operating conditions of superconducting qubits (mK temperatures and low microwave powers). For this purpose, we have developed a broadband measurement setup employing multiplexed lumped element resonators using a broadband power combiner and a low-noise amplifier. The measured temperature and power dependences of the dielectric losses are in good agreement with those predicted for atomic two-level tunneling systems (TLS). By measuring the losses at different frequencies, we found that the TLS density of states is energy dependent. This had not been seen previously in loss measurements. These results contribute to a better understanding of decoherence effects in superconducting qubits and suggest a possibility to minimize TLS-related decoherence by reducing the qubit operation frequency.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4905149