Dresden 2009 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 35: Postersession Transport: Nanoelectronics, Quantum Coherence and Quantum Information, Fluctuations and Noise
TT 35.31: Poster
Mittwoch, 25. März 2009, 14:00–18:00, P1A
Josephson Phase Qubits with Submicron Nb Junctions — Ralf Dolata1, •Jürgen Lisenfeld2, Brigitte Mackrodt1, Alexander Lukashenko2, Alexander Zorin1, and Alexey Ustinov2 — 1Physikalisch-Technische Bundesanstalt, Braunschweig, Germany — 2Physikalisches Institut, Universität Karlsruhe (TH), Karlsruhe, Germany
The microscopic properties of materials including insulating dielectrics and tunnel barriers play a significant role in engineering of Josephson qubits. The use of ultra-small Josephson tunnel junctions should reduce the probability that the macroscopic variable (Josephson phase) couples to parasitic microscopic quantum systems located inside the junction barrier of smaller volume and, therefore, improve the coherence of the qubit. We have fabricated phase qubits applying multilayer Nb technology with lateral dimensions of the junctions of 0.5 µm by 0.5 µm and external on-chip capacitors with either SiO2 or Si3N4 dielectric material. Preliminary measurements of the Rabi oscillations show for the latter samples an increase of the qubit coherence by about a factor of two, whereas generally short coherence times of order 10 ns indicate further decoherence sources being active.