Feedback control of quantum mechanical systems is rapidly attractingattention not only due to fundamental questions about quantum measurements butalso because of its novel applications in many fields in physics. Quantumcontrol has been studied intensively in quantum optics but recently progresshas been made in the control of solid-state qubits as well. In quantumtransport only a few active and passive feedback experiments have been realizedon the level of single-electrons, though theoretical proposals exist. Here wedemonstrate the suppression of shot noise in a single-electron transistor,using an exclusively electronic closed-loop feedback to monitor and adjust thecounting statistics. With increasing feedback response we observe a strongersuppression and faster freezing of charge current fluctuations. Our techniqueis analog to the generation of squeezed light with in-loop photodetection asused in quantum optics. Sub-Poisson single-electron sources will pave the wayfor high precision measurements in quantum transport similar to its optical oropto-mechanical equivalent.
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