The dot can be filled with electrons and then raised in energy. By a process known as 'back-tunneling', all but one of the electrons fall out of the quantum dot back into the source lead. Ideally, just one electron remains trapped in the dot, which is ejected into the output lead by tilting the trap. When this is repeated rapidly this gives a current determined solely by the repetition rate and the charge on each electron a universal constant of nature and the same for all electrons.
The research makes significant steps towards redefining the ampere by developing the application of an electron pump which improves accuracy rates in primary electrical measurement.
Masaya Kataoka of the Quantum Detection Group at NPL said.
"Our device is like a water pump in that it produces a flow by a cyclical action. The tricky part is making sure that exactly the same number of electronic charge is transported in each cycle."
"The way that the electrons in our device behave is quite similar to water; if you try and scoop up a fixed volume of water, say in a cup or spoon, you have to move slowly otherwise you'll spill some. This is exactly what used to happen to our electrons if we went too fast."
Stephen Giblin part of the Quantum Detection Group at NPL said:
"For the last few years, we have worked on optimising the design of our device, but we made a huge leap forward when we fine-tuned the timing sequence. We've basically smashed the record for the largest accurate single-electron current by a factor of 300.
Although moving electrons one at a time is not new, we can do it much faster, and with very high reliability - a billion electrons per second, with an accuracy of less than one error in a million operations.
Using mechanical forces t
|Contact: Natasha Warren|
National Physical Laboratory