Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 1: Superconductivity: Tunnelling, Josephson Junctions, SQUIDs

TT 1.5: Talk

Monday, March 27, 2006, 10:30–10:45, HSZ 02

Low frequency noise in shadow evaporated Josephson junctions — •Jonathan Eroms, L.C. van Schaarenburg, E. Driessen, K. Huizinga, J.H. Plantenberg, R.N. Schouten, A.H. Verbruggen, C.J.P.M. Harmans, and J.E. Mooij — Kavli Institute of Nanoscience Delft, TU Delft, The Netherlands

Shadow angle evaporation is a convenient technique to fabricate sub-micron size tunnel junctions for various applications in mesoscopic physics. Particularly, many realizations of superconducting qubits, both in the charge and flux regime, are manufactured in this way. Now that external sources of decoherence are well understood and increasingly well controlled, the intrinsic limitations of the junction technology become more important. We therefore measured the low frequency resistance fluctuations of a number of small Josephson junctions fabricated in the same manner as our flux qubits. While the low-frequency noise has a 1/f spectral density and drops sharply from room temperature down to about 5 K, the low temperature behavior down to 300 mK is always dominated by a small number of strong two-level fluctuators, and the noise strength saturates between 1 K and 600 mK. The consequences for qubit decoherence are discussed.