Electron transport in nanoscale structures is strongly influenced by the Coulomb interactionthat gives rise to correlations in the stream of charges and leaves clear fingerprints in thefluctuations of the electrical current. A complete understanding of the underlying physicalprocesses requires measurements of the electrical fluctuations on all time and frequencyscales, but experiments have so far been restricted to fixed frequency ranges, as broadbanddetection of current fluctuations is an inherently difficult experimental procedure. Here wedemonstrate that the electrical fluctuations in a single-electron transistor can be accuratelymeasured on all relevant frequencies using a nearby quantum point contact for on-chip realtime detection of the current pulses in the single-electron device. We have directly measuredthe frequency-dependent current statistics and, hereby, fully characterized the fundamentaltunnelling processes in the single-electron transistor. Our experiment paves the way for futureinvestigations of interaction and coherence-induced correlation effects in quantum transport.
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