Single-electron circuits allow control of single charge quanta (electrons) in electronic circuits (Single-Electron Transport = SET). Their function is based on the Coulomb blockade effect, which is the electrostatic effect of repulsion with equal sign. In extremely small, typically nanostructured, circuits this effect becomes so strong that it can be exploited experimentally at very low temperatures (typically a few thousandths of a degree above absolute zero).
Special SET circuits, so-called single electron pumps, enable the generation of electrical currents via clocked transport of individual electrons. Recent advances in this field allow the generation of currents > 100 pA with relative uncertainties of one part in a million and better. Another type of SET circuits, called single-electron transistors, enables the detection of single electrons. Combinations of both types of SET-circuits enable new applications for fundamental metrological research.
Generation of electric currents with a single electron pump, schematically symbolized by a toothed wheel. Individual electrons (yellow) are clocked through the circuit at repetition frequency f. According to the definition of electrical current as an electrical charge flowing per unit time, this results in a current ISET = e.f, with the elementary charge e (charge of an electron).
The working group is involved in the exploitations of these effects for metrological applications, such as the future quantum-based representation of the ampere and the realization of the "Quantum Metrological Triangle".
A survey on the state of research on SET circuits is provided by the following review article:
- J. P. Pekola, O.-P. Saira, V. F. Maisi, A. Kemppinen, M. Möttönen, Y. A. Pashkin, D. V. Averin, „Single-electron current sources: Toward a refined definition of the ampere“, Rev. Mod. Phys. 85, 1421 (2013)