Key points are not available for this paper at this time.
We have operated a five-junction electron pump with an error for transferring electrons of approximately 0. 5 part per 10^6. The error predicted from existing theory is several orders of magnitude smaller, thus implying that our present understanding of the Coulomb blockade is incomplete. We conjecture that the errors arise from photon-assisted tunneling, where the photon energy is supplied by noise from the environment.
Martinis et al. (Mon,) studied this question.