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Using standard microfabrication techniques, it is now possible to construct devices that appear to reliably manipulate electrons one at a time. These devices have potential use as building blocks in quantum computing devices, or as a standard of electrical current derived only from a frequency and the fundamental charge. To date, the error rate in semiconductor 'tuneable-barrier' pump devices, those which show most promise for high-frequency operation, have not been tested in detail. We present high-accuracy measurements of the current from an etched GaAs quantum dot pump, operated at zero source-drain bias voltage with a single ac-modulated gate at 340MHz driving the pump cycle. By comparison with a reference current derived from primary standards, we show that the electron transfer accuracy is better than 15 parts per million. Highresolution studies of the dependence of the pump current on the quantum dot tuning parameters also reveal possible deviations from a model used to describe the pumping cycle. [ABSTRACT FROM AUTHOR]

We demonstrate single-electron pumping in a gate-defined carbon nanotube double quantum dot. By periodic modulation of the potentials of the two quantum dots, we move the system around charge triple points and transport exactly one electron or hole per cycle. We investigate the pumping as a function of the modulation frequency and amplitude and observe good current quantization up to frequencies of 18 MHz where rectification effects cause the mechanism to break down. [ABSTRACT FROM AUTHOR]

The authors demonstrate the feasibility of ballistic electron spectroscopy as a tool for mesoscopic physics. A quantum dot is utilized as an energy-selective detector of nonequilibrium ballistic electrons injected into a two-dimensional electron system. In this letter they use a second quantum dot as the electron injector to evaluate the scheme. They propose an application in the study of interacting one- and zero-dimensional systems. [ABSTRACT FROM AUTHOR]

We present a thermometry scheme to extract the temperature of a two-dimensional electron gas by monitoring the charge occupation of a weakly tunnel-coupled 'thermometer' quantum dot using a quantum point contact detector. Electronic temperatures between 120 and 951 mK are measured with an accuracy of better than 1 mK in the best case, and agree with the lattice temperature measured by a resistance thermometer. The thermometer is non-invasive and does not pass a current through the electron system being measured. The tuning is independent of temperature, and the device is robust in a magnetic field up to 5.6 T. [ABSTRACT FROM AUTHOR]