Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

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.