Atomic Tunneling Systems in Superconducting Quantum Devices
by Prof. Jurgen Lisenfeld
(Kit), Karlsruhe, Germany
at Condensed Matter Seminar
Mon, 11 Jan 2021, 11:30
Sacta-Rashi Building for Physics (54), room 207
Superconducting circuits have demonstrated a tremendous potential to realize integrated quantum computing processors. However, their coherence is strongly reduced by structural material defects which form a bath of parasitic two-state tunnelling systems, so-called TLS . Although TLS were already revealed in the 1970s, encompassing theory and microscopic models are still missing.
The talk will begin with a review of the standard TLS model and its main limitations. The second part will introduce superconducting quantum bits, and show how they can be used to observe and coherently manipulate TLS individually. We report on our experiments where TLS are tuned by applied mechanical strain and electric fields, which reveals their mutual interactions and location in the quantum circuit .
 C Müller et al., Towards understanding two-level-systems in amorphous solids-insights from quantum circuits, Rep. Prog. Phys. 82, 124501 (2019)
 J. Lisenfeld et al., Electric field spectroscopy of material defects in transmon qubits, npj Quantum Inf. 5, 105 (2019)
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