Switchyard for single electrons

February 25, 2008

German scientists achieved to transfer very small charge "packets", comprising a well-defined number of few electrons, between metallic electrons precisely by using a single-electron pump. A single-electron transistor, being able to resolve charge variations of a single electron or less, served as a charge detector to monitor the charge movement. The successful experiment is an important milestone on the way to the setup of a new standard for capacitance, where a capacitor is charged by a well-known number of electrons.

The corresponding voltage can be measured using a Josephson voltage standard. Tracing the capacitance to a resistance via the quantum-Hall effect finally allows the realisation of the so-called "Quantum Metrological Triangle", which establishes a link between all three electrical quantum effects. The precision aimed at in the experiment requires the demonstrated manipulation of charge on the scale of a single electron.

Task of this metrology project is the implementation of a new capacitance standard which is based on the quantization of electrical charge in units ofthe elementary charge e.

The basic idea of the experiment is to charge a capacitor with a well-known number of n electrons and to measure the resulting electrical voltage U. Thus, the capacitance C of the capacitor is determined by C = ne / U. Accurate "counting" of the electrons occurs with the help of a special Single-Electron Tunneling (SET) circuit, a so-called SET-pump. If the voltage U is measured by using a Josephson voltage standard (U = ifh / 2e), the capacitance C can be expressed exclusively in terms of the fundamental constants e and h, the frequency f and integer numbers (n and i). Thus, the experiment enables electrical capacitance metrology on quantum basis, as it is already usual for the electrical voltage U (using the Josephson effect) and the electrical resistance R(using the quantum Hall effect).

If the experiment is performed with a relative uncertainty of 10-7 (0.1 ppm), it opens a way to realize the "quantum metrological triangle" which is a consistency test for the three electrical quantum effects involved. The results of this experiment will impact on a future system of units which will be based on fundamental constants.

Source: Physikalisch-Technische Bundesanstalt

Explore further: New micro-supercapacitor structure inspired by the intricate design of leaves

Related Stories

New technique for 'seeing' ions at work in a supercapacitor

June 22, 2015

Researchers from the University of Cambridge, together with French collaborators based in Toulouse, have developed a new method to see inside battery-like devices known as supercapacitors at the atomic level. The new method ...

Wearables may get boost from boron-infused graphene

May 18, 2015

A microsupercapacitor designed by scientists at Rice University that may find its way into personal and even wearable electronics is getting an upgrade. The laser-induced graphene device benefits greatly when boron becomes ...

Recommended for you

ATLAS and CMS experiments shed light on Higgs properties

September 1, 2015

Three years after the announcement of the discovery of a new particle, the so-called Higgs boson, the ATLAS and CMS Collaborations present for the first time combined measurements of many of its properties, at the third annual ...

Tiny drops of early universe 'perfect' fluid

September 1, 2015

The Relativistic Heavy Ion Collider (RHIC), a particle collider for nuclear physics research at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, smashes large nuclei together at close to the speed of ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.