Quantum constraints on technological superconductors

The regime of rapid thermal activation is addressed in prototype Bi2Sr2CaCu2Ox/Ag tapes containing splayed columnar defects. Although the thermally-activated decay of current diminishes greatly, significant rates of temperature-independent current decay remain due to quantum tunneling of vortices between strong pinning centers. The quantum process dominates the vortex dynamics up to 10 K or more and considerably limits long term current transport in the sample materials.