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Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.1: Vortrag

Mittwoch, 3. April 2019, 09:30–09:45, H48

Coherence of a transmon qubit under in-plane magnetic fields — •Andre Schneider1, Alexey V. Ustinov1,2, and Martin Weides1,31Karlsruhe Institute of Technology, Karlsruhe, Germany — 2National University of Science and Technology MISIS, Moscow, Russia — 3University of Glasgow, Glasgow, United Kingdom

Superconducting quantum circuits are versatile building elements for quantum technologies, with applications ranging from computing and simulation to sensing and metrology. The extreme sensitivity of SQUIDs to magnetic fields is used in many technological applications, and new quantum sensing schemes like the detection of amplitude and frequency of microwave signals by a superconducting transmon qubit [1] are being developed.

To identify possible fields of application, we investigate the environmental magnetic conditions for the usability of such a qubit. By placing a transmon qubit in a magnetic field, we analyze its transition frequency and coherence properties. We find that the transition frequency strongly depends on the flux penetrating the Al/AlOx/Al Josephson junction and can be modeled precisely as function of the in-plane magnetic field. We demonstrate quantum coherence up to field values of 40 mT with qubit lifetimes of T1 0.5 µ s and find corresponding T2 times resulting in a constant pure dephasing rate at any field. The possibility to operate superconducting qubits in magnetic fields far beyond the critical field of the bulk superconductor opens new avenues, for instance in quantum sensing and metrology.
A. Schneider et al., Phys. Rev. A 97, 062334 (2018)

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