Berlin 2018 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 4: Superconductivity: Qubits I
TT 4.6: Vortrag
Montag, 12. März 2018, 10:45–11:00, H 2053
Flux-Noise Spectroscopy on a Superconducting Transmon Qubit — •Tim Wolz1, Andre Schneider1, Jochen Braumüller1, Alexey V. Ustinov1,2, and Martin Weides1,3 — 1Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany — 2Russian Quantum Center, Moscow, Russia — 3Institut für Physik, Johannes Gutenberg Universität, Mainz, Germany
Superconducting qubits can act as noise sensors because their decoherence times under certain pulse sequences can be linked to the system’s noise power spectral density (PSD). These sequences also set the observable frequency range of the PSD. The PSD during free evolution of the qubit can be obtained with a dynamical decoupling (CPMG-) pulse sequence, which renders the qubit only susceptible to noise within a narrow frequency band. The PSD during driven evolution is measured with a so-called spin-locking sequence, during which only noise at the Rabi frequency can affect the qubit. Both protocols were successfully tested on a flux qubit by Bylander [1] and Yan [2]. In this work, we apply these two protocols to a tunable concentric transmon [3], overcome the challenge of the transmon’s low anharmonicity by using DRAG pulses and compare the PSDs of free and driven evolution. Our results show a clear 1/f dependence in both cases, as well as a white spectrum at frequencies above 1 MHz during free evolution. The successful application of these protocols to a transmon permits magnetic noise sensing with such a qubit in future experiments.
J. Bylander et al., Nat. Phys. (2011).
F. Yan et al., Nat. Comm. (2013).
J. Braumüller et al., Appl. Phys. Lett. (2016)