Leakage and counting errors in a seven-junction electron pump

Leakage and counting errors are explored experimentally in a well-characterized seven-junction electron pump and compared with predictions of the orthodox theory, including cotunneling. Theory and experiment are in good agreement at intermediate temperatures, where errors are dominated by thermally activated, single-junction processes. At low temperatures, however, the observed errors far exceed predictions, indicating that the orthodox theory omits an important error process.