Regensburg 2019 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 40: Superconductivity: Qubits 1
TT 40.2: Vortrag
Mittwoch, 3. April 2019, 09:45–10:00, H48
What Can Be Learned from Measuring Quantum Jumps of a Transmon Qubit? — •Dennis Rieger1, Patrick Winkel1, Ivan Takmakov1,2, Luca Planat3, Farshad Foroughi3, Wiebke Hasch-Guichard3, Kiril Borisov2, Julian Ferrero1, Lukas Grünhaupt1, Daria Gusenkova1, Fabio Henriques1, Nataliya Maleeva1, Alexey V. Ustinov1, Wolfgang Wernsdorfer1,2,3, Nicolas Roch3, and Ioan M. Pop1,2 — 1Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — 2Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany — 3Institut Néel, CNRS and Université Joseph Fourier, Grenoble, France
Resolving quantum jumps of superconducting qubits requires fast, high-fidelity readout, which can be enabled by a superconducting parametric amplifier as a first amplifier stage for the readout signal. We use the Dimer Josephson Junction Array Amplifier (DJJAA) to measure quantum jump traces of a transmon qubit dispersively coupled to a readout resonator and placed inside a 3D waveguide.
The measured coherence times of the transmon are sufficiently long compared to the integration time needed for qubit state discrimination. The quantum jumps follow Poisson statistics and we find that the T1 during readout is significantly reduced compared to the free evolution T1. Also, the effective qubit temperature saturates at approximately 50 mK even though the qubit is thermally anchored to the mixing chamber stage of a dilution refrigerator at 20 mK.