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TT: Fachverband Tiefe Temperaturen

TT 4: Superconductivity: Qubits I

TT 4.9: Vortrag

Montag, 12. März 2018, 11:45–12:00, H 2053

Decoherence mechanisms in transmon qubits:
Ultra-low frequency noise and switching events
— •Steffen Schlör¹, Andre Schneider¹, Jürgen Lisenfeld¹, Martin Sandberg², David P. Pappas², Alexey V. Ustinov¹, and Martin Weides^1,3 — ¹Physikalisches Institut, Karlsruhe Institute of Technology, Germany — ²National Institute of Standards and Technology, Boulder, USA — ³Institute of Physics, Johannes Gutenberg University Mainz, Germany

Today’s quantum computers made of highly coherent superconducting qubits are already capable to find the electronic ground state of small molecules [1]. The complexity and number of qubits on single chips having gate fidelities at or beyond the threshold for fault-tolerant quantum computing [2] keeps growing. Their longer operation times shift the focus towards decoherence mechanisms and fluctuations occurring on time scales of hours or even days.

We present the results of such long-term measurements of a high-coherent, non-tunable transmon qubit. We perform simultaneous measurements of the qubit’s relaxation and dephasing rates as well as resonance frequency shifts and analyze their correlations. These yield information about the microscopic origin of decoherence mechanisms, their interacting with the qubit, and their fluctuation dynamics. From a spectral noise analysis, we obtain evidence for the presence of a small number of dominant fluctuators.
A. Kandala et al., Nature 549(7671), 2017
R. Barends et al., Nature 508(7497), 2014