Conditional statistics of electron transport in interacting nanoscale conductors

There is an intimate connection between the acquisition of information and how this information changes the remaining uncertainty in the system. This trade-off between information and uncertainty plays a central role in the context of detection. Recent advances in the ability to make accurate, on-chip measurements of individual-electron current through a quantum dot(1-8) (QD) have been enabled by exploiting the sensitivity of a second current, passing through a nearby quantum point contact (QPC), to the fluctuating charge on the QD(4-8). An important characteristic of QPC detectors is their minimal influence on the systems they probe. Here we show that even the operation of an effectively non-invasive QPC detector can statistically alter the system's behaviour. By observing a particular QPC current, the statistical distribution of the QD conditional current undergoes a substantial change in comparison to that expected for unconditional shot noise(9). These results are in almost perfect agreement with a theoretical model we develop to predict the joint current probability distribution and conditional transport statistics of interacting nanoscale systems.