Two NPL employees gave presentations at the International Conference on the Physics of Semiconductors 2012, which was held at ETH Zurich. Masaya Kataoka  presented his work demonstrating the massive improvement in the accuracy of a single electron pump that is achieved when tuning the quantum dot decoupling time. This enables  the 'back-tunneling' time  to be varied independently of the repetition rate i.e. increasing the time when we carefully allow excess to leave, while keeping the same repetition rate.

The audience were impressed by the measurement techniques that were implemented to accurately measure the pump accuracy (current accurate to 1.2 ppm @1GHz repetition rate, ~160pA). This work also included high accuracy measurements of the pumps current. (This work was featured in Nature Communications, presented in last month’s knowledge report)

Also Jon Fletcher gave a talk about our recent measurements of the energy and time spread of the electrons that we eject from our electron pump into a region of two dimensional electron gas. These measurements reveal that the electrons travel ballistically for many microns with rather large kinetic energy, but with very little spreading of the electronic wavefunction. Unlike some other pumps where the time of release of the electron is poorly defined, our electron pump really behaves like a single-electron gun, with very tightly defined release time and energy.

This is important for integration of these pumps into other devices and also reveals information about the energy level structure in the pump confinement region where the single electrons are trapped. Several other groups (including PTB) are competing in the space for 'single-electron' analogues of quantum optics, so this is a fairly hot topic.

Links to the talk abstracts:

http://sciconf.org/icps2012/ip/topic/10/session/23/paper/3

http://sciconf.org/icps2012/ip/topic/10/session/48/paper/4

Contact: Jon Fletcher