Date:9/22/2011

enables the "emission" of individual electrons from the QD, moving them over a specific distance and then detecting them at the neighbouring QD. A distance of four micrometres (μm) was used in the experiment this is twenty times larger than a highly integrated transistor. Targeted transport of individual electrons is possible in the following way: First, a QD is defined between the tips of four electrodes to form this zero-dimensional object, containing some hundred electrons. The scientists subsequently send a sound wave along the semiconductor surface using interdigital (like two combs fitted together without touching each other) electrodes to which they apply a radio frequency voltage. This method functions in the opposite way as the electrical discharge of a piezo ignition system in which a crystal is deformed to attain a voltage. The researchers applied voltage to the crystal and thus deform it, and the alternating voltage leads to the formation of a sound wave.

The fish surfs on the wave

In a sample, this wave moves, for example, from left to right through the quantum dot at the velocity of sound inside the crystal at three kilometres per second. Its height is adjusted so that it extracts exactly one "fish" from it. The latter subsequently surfs on the wave in a one-dimensional channel. The "fish" arrives at the neighbouring quantum dot 4 μm to the right thereof. The researchers were able to attain good statistics by repetition of the waves and measurements and thus capable of determining the reliability of the method. During the first experiments, the probability of emission and detection of a single electron with the wave was 96 and 92%, respectively.

The innovation: aligning the fish

It is not possible to differentiate between the electrons "fish", but they can be differently aligned because they rotate like little spinning tops. This is called the "spin" of the electron. For example one can
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Contact: Prof. Dr. Andreas Wieck andreas.wieck@rub.de 49-234-322-6726 Ruhr-University Bochum Source:Eurekalert

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