Electronic Decoherence of Two-Level Systems in a Josephson Junction
Abstract
The sensitivity of superconducting qubits allows for spectroscopy and coherence measurements on individual two-level systems present in the disordered tunnel barrier of an Josephson junction. We report experimental evidence for the decoherence of two-level systems by Bogoliubov quasiparticles leaking into the insulating barrier. We control the density of quasiparticles in the junction electrodes either by the sample temperature or by injecting them using an on-chip dc-SQUID driven to its resistive state. The decoherence rates were measured by observing the two-level system's quantum state evolving under application of resonant microwave pulses and were found to increase linearly with quasiparticle density, in agreement with theory. This interaction with electronic states provides a noise and decoherence mechanism that is relevant for various microfabricated devices such as qubits, single-electron transistors, and field-effect transistors. The presented experiments also offer a possibility to determine the location of the probed two-level systems across the tunnel barrier, providing clues about the fabrication step in which they emerge.
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Cite
@article{arxiv.1609.06173,
title = {Electronic Decoherence of Two-Level Systems in a Josephson Junction},
author = {Alexander Bilmes and Sebastian Zanker and Andreas Heimes and Michael Marthaler and Gerd Schön and Georg Weiss and Alexey V. Ustinov and Jürgen Lisenfeld},
journal= {arXiv preprint arXiv:1609.06173},
year = {2017}
}