Dresden 2017 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 76: Poster Session: Transport 2

TT 76.4: Poster

Donnerstag, 23. März 2017, 15:00–19:00, P2-OG1

Noise spectroscopy by dynamical decoupling of a transmon qubit — •Tim Wolz, Andre Schneider, Jochen Braumüller, Martin Weides, and Alexey V. Ustinov — Institute of Physics, Karlsruhe Institute of Technology, Germany

Superconducting qubits are promising candidates as elements of quantum computers. Environmental noise limits coherence times of superconducting qubits. Improving coherence times requires a detailed knowledge about noise mechanisms. To obtain the noise power spectral density (PSD) of a qubit system, dynamical decoupling pulse sequences can be employed. Such sequences comprise several gates to refocus dephased qubits and effectively act as frequency filters. Hence, by knowing the properties of the frequency filter and measuring the qubit's state, the noise PSD can be scanned, as it was already shown for a flux qubit [1]. In this work, noise spectroscopy is performed on a tunable concentric transmon qubit [2] by using dynamical decoupling. Because of the low anharmonicity of the transmon, gate errors play a severe role in distorting the qubit's state and subsequently the noise PSD. By using DRAG [3] pulses, we are able to accomplish sufficiently precise gates, and can thus confidently extract the noise PSD. Another advantage of this method is its universality, i.e., no functional form of the PSD needs to be assumed, and hence it can also be applied to environmental magnetic field sensing.

[1] J. Bylander et al., Nature Phys. 7, 565 (2011)

[2] J. Braumueller et al., Appl. Phys. Lett. 108, 032601 (2016)

[3] F. Motzoi et al., Phys. Rev. Lett. 103,110501 (2009)