Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 17: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs

TT 17.1: Vortrag

Montag, 31. März 2014, 15:00–15:15, HSZ 201

Fabrication of a transparent NbAl interface in hybrid Josephson junctions and flux qubits with π-shifters and their low-temperature measurements. — •Anastasia Shcherbakova¹, Kirill Fedorov², Kirill Shulga³, Valery Ryazanov⁴, Vitaly Bol'ginov⁴, Detlef Beckman⁵, and Alexey V. Ustinov^1,2,5 — ¹Physikalisches Institut, Karlsruhe Institut fuer Technologie, D-76131, Karlsruhe, Germany — ²Walther-Meißner-Institut, D-85748, Garching, Germany — ³National University of Science and Technology MISIS, 119049 Moscow, Russian Federation — ⁴Institute of Solid State Physics, Chernogolovka, 142432 Russian Federation — ⁵RQC, BC "Ural", Skolkovo, Moscow region, 143025 Russian Federation

Aluminum-based superconducting flux qubits can be made very compact and employ high-quality Josephson junctions. An external magnetic flux need to be applied in order to set the flux qubit to a working point at minimal frequency. Adding a π-junction to the qubit loop makes applying the magnetic flux unnecessary, thus removing possible source of external fluctuations. The conventional fabrication of π-junctions requires depositing of niobium layers separated by a ferromagnet. We report fabrication of composite Al/Nb flux qubits with Nb/CuNi/Nb junctions embedded in the loop. The π-biased qubits show the characteristic microwave spectrum shifted by a half of a magnetic flux quantum. The reported technological approach opens way to a variety of quantum circuits employing Nb and Al elements.