  We have developed a superconducting phase gradiometer consisting of two
parallel DNA-templated nanowires connecting two thin-film leads. We have ramped
the cross current flowing perpendicular to the nanowires, and observed
oscillations in the lead-to-lead resistance due to cross-current-induced phase
differences. By using this gradiometer we have measured the temperature and
magnetic field dependence of the superfluid density and observed an
amplification of phase gradients caused by elastic vortex displacements. We
examine our data in light of Miller-Bardeen theory of dirty superconductors and
a microscale version of Campbell's model of field penetration.
