Exponentially small quantum correction to conductance

Abstract When time-reversal symmetry is broken, the average conductance through a chaotic cavity, from an entrance lead with N 1 open channels to exit 2 channels, given by / M , where = + . We show that, when tunnel barriers of reflectivity ? are placed on leads, two correction terms appear in conductance, and that one them proportional Since ? ? ?1 this exponentially small semiclassical limit. derive term approximation, generally expected give only leading orders powers Even though theory built perturbatively both 1/ final result exact.