Adiabatic transport of Cooper pairs in arrays of Josephson junctions

Abstract

We have developed a quantitative theory of Cooper pair pumping in gated one-dimensional arrays of Josephson junctions. The pumping accuracy is limited by quantum tunneling of Cooper pairs out of the propagating potential well and by direct supercurrent flow through the array. Both corrections decrease exponentially with the number N of junctions in the array, but give a serious limitation of accuracy for any practical array. The supercurrent at resonant gate voltages decreases with N only as $\mathrm{sin}(\ensuremath{\varphi}/N)/N,$ where $\ensuremath{\varphi}$ is the Josephson phase difference across the array.