Cooper pair transport in arrays of Josephson junctions

In this work, experimental work on one-dimensional small capacitance Josephson junction arrays (1D SCJJAs) is presented. The results help gain a quantitative understanding of the charge transport properties of these 1D SCJJAs, paving the way for applications in quantum metrology and the study of quantum phase transitions. If several small superconducting islands are weakly connected in series, each island is a site for charge localization, and Cooper pairs can tunnel from one to the other. By tuning the tunnel coupling between the islands via SQUIDs, the transport properties can be changed from entirely superconducting to entirely insulating behavior. The insulating behavior is expressed in the current-voltage characteristics as a Coulomb blockade of current. Transport through Coulomb blockaded arrays is activated above a voltage or thermal threshold. The main subject of this work is the study of thermally activated transport at very small bias voltages. 1D SCJJAs have been studied for two decades now. Aspects of the current- voltage characteristics can be explained, but quantitative understanding is still limited. A major advantage of measuring and analyzing the thermally activated conductance at very small bias voltages is the accessability to theoretical modeling. In close collaboration with theoretical groups at the KIT a simple hopping model has been developed and successfully compared with the data measured in the framework of this work.