Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 1: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs
TT 1.4: Vortrag
Montag, 27. März 2006, 10:15–10:30, HSZ 02
Frozen-flux-quanta phase shifter for digital Josephson circuits — •Dmitry Balashov1, M. Khabipov1, D. Hagedorn1, A. B. Zorin1, F.-Im. Buchholz1, J. Niemeyer1, B. Dimov2, Th. Ortlepp2, and F. H. Uhlmann2 — 1Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany — 2Technische Universität Ilmenau, 98684 Ilmenau, Germany
Superconducting Rapid Single Flux Quantum (RSFQ) digital circuits are very promising for integration with Josephson qubits of different types. The basic quantization condition of each RSFQ cell is given by LIc>Φ0 (L is the loop inductance and Φ0 ≈ 2.07 mV·ps is the single flux quantum). For qubit applications, the critical current Ic of the RSFQ circuits should be set to about several µA, which, in turn, requires large geometrical inductance of the loop to ensure a certain phase shift inside or between the cells. The replacement of large inductances by the novel passive phase shifting elements based on small integer numbers of flux quanta frozen in the superconducting loops provides the well-defined phase shift. We report on the experimental verification of operation of such compact passive phase shifter elements realised in standard niobium SIS-trilayer technology for two different critical current densities: jc = 100 A/cm2 (Icmin = 10 µA), and jc = 1 kA/cm2 (Icmin = 125 µA). The flux quanta injection to the phase shifter loops was managed by feeding proper current into specially designed control lines.
This work is supported by DFG (NI253/7-1, UH53/6-1) and the EU (RSFQubit).