Algorithms for automatic measurement of SIS-type hysteretic underdamped Josephson junction's parameters by current-voltage characteristics

Abstract

Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction (JJ) can be measured by its current-voltage characteristics (IVCs). Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments. This leads to the need for multiple measurements with subsequent statistical processing. In this paper, the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC. These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy. The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement. A sequence of current pulses with slow rising and falling edges is used to drive JJ, and synchronous current and voltage readings at JJ are used to realize measurement algorithms. The algorithm performance is estimated through computer simulations. The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters, as well as the simple implementation in automatic digital measuring systems. The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits, which will improve the production efficiency and product quality.