Application of NbSi nanowires for quantum phase slip experiment

A superconducting nanowire of sufficiently small (nanometer scale) cross section is expected to lose phase coherence due to the quantum phase slips (QPS) at low temperatures. The QPS nanowire combined with high impedance environment forms a system dual to the Josephson junction and is suggested to be applicable for a quantum current standard. In analogy to the current-biased Josephson junction this QPS nanowire, biased by voltage below the critical value VC, can be characterized by a washboard potential for the charge variable. Application of ac drive should result in the steps of current, I=2ef, which are dual to Shapiro steps. Using approach similar to ones described in we have developed technology of fabrication of NbSi nanowires with cross sections down to 15 nm by 8 nm integrated with high-ohmic Cr film resistors. The circuits have been characterized at mK temperatures and some of them exhibited characteristic Coulomb blockade behaviour.